From a2b99dcac36c332d4a49184716fc2a67dc1bdbb1 Mon Sep 17 00:00:00 2001 From: Adam Zerella Date: Sat, 28 Sep 2019 22:58:19 +1000 Subject: docs: arm64: Fix indentation and doc formatting Sphinx generates the following warnings for the arm64 doc pages: Documentation/arm64/memory.rst:158: WARNING: Unexpected indentation. Documentation/arm64/memory.rst:162: WARNING: Unexpected indentation. These indentations warnings can be resolved by utilising code hightlighting instead. Signed-off-by: Adam Zerella Signed-off-by: Will Deacon --- Documentation/arm64/memory.rst | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) (limited to 'Documentation') diff --git a/Documentation/arm64/memory.rst b/Documentation/arm64/memory.rst index b040909e45f8..02e02175e6f5 100644 --- a/Documentation/arm64/memory.rst +++ b/Documentation/arm64/memory.rst @@ -154,11 +154,18 @@ return virtual addresses to userspace from a 48-bit range. Software can "opt-in" to receiving VAs from a 52-bit space by specifying an mmap hint parameter that is larger than 48-bit. + For example: - maybe_high_address = mmap(~0UL, size, prot, flags,...); + +.. code-block:: c + + maybe_high_address = mmap(~0UL, size, prot, flags,...); It is also possible to build a debug kernel that returns addresses from a 52-bit space by enabling the following kernel config options: + +.. code-block:: sh + CONFIG_EXPERT=y && CONFIG_ARM64_FORCE_52BIT=y Note that this option is only intended for debugging applications -- cgit From 3a24f7f6b610910ee328df11392e21925cefdecb Mon Sep 17 00:00:00 2001 From: Cristian Marussi Date: Thu, 26 Sep 2019 18:52:18 +0100 Subject: kselftest: add capability to skip chosen TARGETS Let the user specify an optional TARGETS skiplist through the new optional SKIP_TARGETS Makefile variable. It is easier to skip at will using a reduced and well defined list of possibly problematic targets with SKIP_TARGETS than to provide a partially stripped down list of good targets using the usual TARGETS variable. Signed-off-by: Cristian Marussi Signed-off-by: Shuah Khan --- Documentation/dev-tools/kselftest.rst | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) (limited to 'Documentation') diff --git a/Documentation/dev-tools/kselftest.rst b/Documentation/dev-tools/kselftest.rst index 25604904fa6e..ecdfdc9d4b03 100644 --- a/Documentation/dev-tools/kselftest.rst +++ b/Documentation/dev-tools/kselftest.rst @@ -89,6 +89,22 @@ To build, save output files in a separate directory with KBUILD_OUTPUT :: $ export KBUILD_OUTPUT=/tmp/kselftest; make TARGETS="size timers" kselftest +Additionally you can use the "SKIP_TARGETS" variable on the make command +line to specify one or more targets to exclude from the TARGETS list. + +To run all tests but a single subsystem:: + + $ make -C tools/testing/selftests SKIP_TARGETS=ptrace run_tests + +You can specify multiple tests to skip:: + + $ make SKIP_TARGETS="size timers" kselftest + +You can also specify a restricted list of tests to run together with a +dedicated skiplist:: + + $ make TARGETS="bpf breakpoints size timers" SKIP_TARGETS=bpf kselftest + See the top-level tools/testing/selftests/Makefile for the list of all possible targets. -- cgit From 43fd0cf4c6dcd5a0e383e60168428bda0bc56374 Mon Sep 17 00:00:00 2001 From: Lukas Zapletal Date: Mon, 23 Sep 2019 12:59:31 +0200 Subject: hwmon: (k10temp) Update documentation and add temp2_input info It's been a while since the k10temp documentation has been updated. There are new CPU families supported as well as Tdie temp was added. This patch adds all missing families which I was able to find from git history and provides more info about Tctl vs Tdie exported temps. Signed-off-by: Lukas Zapletal Link: https://lore.kernel.org/r/20190923105931.27881-1-lzap+git@redhat.com [groeck: Formatting] Signed-off-by: Guenter Roeck --- Documentation/hwmon/k10temp.rst | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) (limited to 'Documentation') diff --git a/Documentation/hwmon/k10temp.rst b/Documentation/hwmon/k10temp.rst index 12a86ba17de9..4451d59b9425 100644 --- a/Documentation/hwmon/k10temp.rst +++ b/Documentation/hwmon/k10temp.rst @@ -21,10 +21,17 @@ Supported chips: * AMD Family 14h processors: "Brazos" (C/E/G/Z-Series) -* AMD Family 15h processors: "Bulldozer" (FX-Series), "Trinity", "Kaveri", "Carrizo" +* AMD Family 15h processors: "Bulldozer" (FX-Series), "Trinity", "Kaveri", + "Carrizo", "Stoney Ridge", "Bristol Ridge" * AMD Family 16h processors: "Kabini", "Mullins" +* AMD Family 17h processors: "Zen", "Zen 2" + +* AMD Family 18h processors: "Hygon Dhyana" + +* AMD Family 19h processors: "Zen 3" + Prefix: 'k10temp' Addresses scanned: PCI space @@ -110,3 +117,12 @@ The maximum value for Tctl is available in the file temp1_max. If the BIOS has enabled hardware temperature control, the threshold at which the processor will throttle itself to avoid damage is available in temp1_crit and temp1_crit_hyst. + +On some AMD CPUs, there is a difference between the die temperature (Tdie) and +the reported temperature (Tctl). Tdie is the real measured temperature, and +Tctl is used for fan control. While Tctl is always available as temp1_input, +the driver exports Tdie temperature as temp2_input for those CPUs which support +it. + +Models from 17h family report relative temperature, the driver aims to +compensate and report the real temperature. -- cgit From b428db1e880d5f0f1cc22009974bee38a095284e Mon Sep 17 00:00:00 2001 From: Adam Zerella Date: Wed, 25 Sep 2019 23:17:15 +1000 Subject: docs: hwmon: Include 'inspur-ipsps1.rst' into docs When generating documentation output Sphinx outputs a warning for not including the page 'inspur-ipsps1.rst' in 'index.rst'. Assuming this documentation is useful it should be included in the index. Signed-off-by: Adam Zerella Link: https://lore.kernel.org/r/20190925131715.GB19073@gmail.com Signed-off-by: Guenter Roeck --- Documentation/hwmon/index.rst | 1 + 1 file changed, 1 insertion(+) (limited to 'Documentation') diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst index 8147c3f218bf..230ad59b462b 100644 --- a/Documentation/hwmon/index.rst +++ b/Documentation/hwmon/index.rst @@ -7,6 +7,7 @@ Linux Hardware Monitoring hwmon-kernel-api pmbus-core + inspur-ipsps1 submitting-patches sysfs-interface userspace-tools -- cgit From 015664d15270a112c2371d812f03f7c579b35a73 Mon Sep 17 00:00:00 2001 From: Bastien Nocera Date: Mon, 23 Sep 2019 18:18:43 +0200 Subject: USB: rio500: Remove Rio 500 kernel driver The Rio500 kernel driver has not been used by Rio500 owners since 2001 not long after the rio500 project added support for a user-space USB stack through the very first versions of usbdevfs and then libusb. Support for the kernel driver was removed from the upstream utilities in 2008: https://gitlab.freedesktop.org/hadess/rio500/commit/943f624ab721eb8281c287650fcc9e2026f6f5db Cc: Cesar Miquel Signed-off-by: Bastien Nocera Cc: stable Link: https://lore.kernel.org/r/6251c17584d220472ce882a3d9c199c401a51a71.camel@hadess.net Signed-off-by: Greg Kroah-Hartman --- Documentation/usb/rio.rst | 109 ---------------------------------------------- 1 file changed, 109 deletions(-) delete mode 100644 Documentation/usb/rio.rst (limited to 'Documentation') diff --git a/Documentation/usb/rio.rst b/Documentation/usb/rio.rst deleted file mode 100644 index ea73475471db..000000000000 --- a/Documentation/usb/rio.rst +++ /dev/null @@ -1,109 +0,0 @@ -============ -Diamonds Rio -============ - -Copyright (C) 1999, 2000 Bruce Tenison - -Portions Copyright (C) 1999, 2000 David Nelson - -Thanks to David Nelson for guidance and the usage of the scanner.txt -and scanner.c files to model our driver and this informative file. - -Mar. 2, 2000 - -Changes -======= - -- Initial Revision - - -Overview -======== - -This README will address issues regarding how to configure the kernel -to access a RIO 500 mp3 player. -Before I explain how to use this to access the Rio500 please be warned: - -.. warning:: - - Please note that this software is still under development. The authors - are in no way responsible for any damage that may occur, no matter how - inconsequential. - -It seems that the Rio has a problem when sending .mp3 with low batteries. -I suggest when the batteries are low and you want to transfer stuff that you -replace it with a fresh one. In my case, what happened is I lost two 16kb -blocks (they are no longer usable to store information to it). But I don't -know if that's normal or not; it could simply be a problem with the flash -memory. - -In an extreme case, I left my Rio playing overnight and the batteries wore -down to nothing and appear to have corrupted the flash memory. My RIO -needed to be replaced as a result. Diamond tech support is aware of the -problem. Do NOT allow your batteries to wear down to nothing before -changing them. It appears RIO 500 firmware does not handle low battery -power well at all. - -On systems with OHCI controllers, the kernel OHCI code appears to have -power on problems with some chipsets. If you are having problems -connecting to your RIO 500, try turning it on first and then plugging it -into the USB cable. - -Contact Information -------------------- - - The main page for the project is hosted at sourceforge.net in the following - URL: . You can also go to the project's - sourceforge home page at: . - There is also a mailing list: rio500-users@lists.sourceforge.net - -Authors -------- - -Most of the code was written by Cesar Miquel . Keith -Clayton is incharge of the PPC port and making sure -things work there. Bruce Tenison is adding support -for .fon files and also does testing. The program will mostly sure be -re-written and Pete Ikusz along with the rest will re-design it. I would -also like to thank Tri Nguyen who provided use -with some important information regarding the communication with the Rio. - -Additional Information and userspace tools - - http://rio500.sourceforge.net/ - - -Requirements -============ - -A host with a USB port running a Linux kernel with RIO 500 support enabled. - -The driver is a module called rio500, which should be automatically loaded -as you plug in your device. If that fails you can manually load it with - - modprobe rio500 - -Udev should automatically create a device node as soon as plug in your device. -If that fails, you can manually add a device for the USB rio500:: - - mknod /dev/usb/rio500 c 180 64 - -In that case, set appropriate permissions for /dev/usb/rio500 (don't forget -about group and world permissions). Both read and write permissions are -required for proper operation. - -That's it. The Rio500 Utils at: http://rio500.sourceforge.net should -be able to access the rio500. - -Limits -====== - -You can use only a single rio500 device at a time with your computer. - -Bugs -==== - -If you encounter any problems feel free to drop me an email. - -Bruce Tenison -btenison@dibbs.net -- cgit From 0aa760382040cc3d70b538ade56ba9c37ed8b702 Mon Sep 17 00:00:00 2001 From: Jonathan Neuschäfer Date: Thu, 3 Oct 2019 21:31:32 +0200 Subject: dt-bindings: usb: Fix references to usb-hcd.yaml MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit usb-hcd.txt has been converted to YAML. Update references accordingly. Fixes: 14ec072a19ad ("dt-bindings: usb: Convert USB HCD generic binding to YAML") Signed-off-by: Jonathan Neuschäfer Link: https://lore.kernel.org/r/20191003193132.17758-1-j.neuschaefer@gmx.net Signed-off-by: Greg Kroah-Hartman --- Documentation/devicetree/bindings/usb/mediatek,mtk-xhci.txt | 4 ++-- Documentation/devicetree/bindings/usb/mediatek,mtu3.txt | 4 ++-- Documentation/devicetree/bindings/usb/usb-uhci.txt | 2 +- Documentation/devicetree/bindings/usb/usb-xhci.txt | 4 ++-- 4 files changed, 7 insertions(+), 7 deletions(-) (limited to 'Documentation') diff --git a/Documentation/devicetree/bindings/usb/mediatek,mtk-xhci.txt b/Documentation/devicetree/bindings/usb/mediatek,mtk-xhci.txt index f3e4acecabe8..42d8814f903a 100644 --- a/Documentation/devicetree/bindings/usb/mediatek,mtk-xhci.txt +++ b/Documentation/devicetree/bindings/usb/mediatek,mtk-xhci.txt @@ -33,7 +33,7 @@ Required properties: "dma_ck": dma_bus clock for data transfer by DMA, "xhci_ck": controller clock - - phys : see usb-hcd.txt in the current directory + - phys : see usb-hcd.yaml in the current directory Optional properties: - wakeup-source : enable USB remote wakeup; @@ -53,7 +53,7 @@ Optional properties: See: Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt - imod-interval-ns: default interrupt moderation interval is 5000ns -additionally the properties from usb-hcd.txt (in the current directory) are +additionally the properties from usb-hcd.yaml (in the current directory) are supported. Example: diff --git a/Documentation/devicetree/bindings/usb/mediatek,mtu3.txt b/Documentation/devicetree/bindings/usb/mediatek,mtu3.txt index b9af7f5ee91d..e0ae6096f7ac 100644 --- a/Documentation/devicetree/bindings/usb/mediatek,mtu3.txt +++ b/Documentation/devicetree/bindings/usb/mediatek,mtu3.txt @@ -17,7 +17,7 @@ Required properties: - clock-names : must contain "sys_ck" for clock of controller, the following clocks are optional: "ref_ck", "mcu_ck" and "dma_ck"; - - phys : see usb-hcd.txt in the current directory + - phys : see usb-hcd.yaml in the current directory - dr_mode : should be one of "host", "peripheral" or "otg", refer to usb/generic.txt @@ -60,7 +60,7 @@ Optional properties: - mediatek,u3p-dis-msk : mask to disable u3ports, bit0 for u3port0, bit1 for u3port1, ... etc; -additionally the properties from usb-hcd.txt (in the current directory) are +additionally the properties from usb-hcd.yaml (in the current directory) are supported. Sub-nodes: diff --git a/Documentation/devicetree/bindings/usb/usb-uhci.txt b/Documentation/devicetree/bindings/usb/usb-uhci.txt index cc2e6f7d602e..d1702eb2c8bd 100644 --- a/Documentation/devicetree/bindings/usb/usb-uhci.txt +++ b/Documentation/devicetree/bindings/usb/usb-uhci.txt @@ -6,7 +6,7 @@ Required properties: - reg : Should contain 1 register ranges(address and length) - interrupts : UHCI controller interrupt -additionally the properties from usb-hcd.txt (in the current directory) are +additionally the properties from usb-hcd.yaml (in the current directory) are supported. Example: diff --git a/Documentation/devicetree/bindings/usb/usb-xhci.txt b/Documentation/devicetree/bindings/usb/usb-xhci.txt index 97400e8f8605..b49b819571f9 100644 --- a/Documentation/devicetree/bindings/usb/usb-xhci.txt +++ b/Documentation/devicetree/bindings/usb/usb-xhci.txt @@ -41,9 +41,9 @@ Optional properties: - usb3-lpm-capable: determines if platform is USB3 LPM capable - quirk-broken-port-ped: set if the controller has broken port disable mechanism - imod-interval-ns: default interrupt moderation interval is 5000ns - - phys : see usb-hcd.txt in the current directory + - phys : see usb-hcd.yaml in the current directory -additionally the properties from usb-hcd.txt (in the current directory) are +additionally the properties from usb-hcd.yaml (in the current directory) are supported. -- cgit From 976392650a00651ea29f64c5dc54f059aa54e0d1 Mon Sep 17 00:00:00 2001 From: Mauro Carvalho Chehab Date: Tue, 24 Sep 2019 10:01:29 -0300 Subject: bindings: rename links to mason USB2/USB3 DT files Those files got renamed, but another DT file still points to the older places. Fixes: 87a55485f2fc ("dt-bindings: phy: meson-g12a-usb3-pcie-phy: convert to yaml") Fixes: da86d286cce8 ("dt-bindings: phy: meson-g12a-usb2-phy: convert to yaml") Signed-off-by: Mauro Carvalho Chehab Acked-by: Rob Herring Link: https://lore.kernel.org/r/9ca2d136a1f79c878fff1208f9b536b0b613c0d5.1569330078.git.mchehab+samsung@kernel.org Signed-off-by: Greg Kroah-Hartman --- Documentation/devicetree/bindings/usb/amlogic,dwc3.txt | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'Documentation') diff --git a/Documentation/devicetree/bindings/usb/amlogic,dwc3.txt b/Documentation/devicetree/bindings/usb/amlogic,dwc3.txt index b9f04e617eb7..6ffb09be7a76 100644 --- a/Documentation/devicetree/bindings/usb/amlogic,dwc3.txt +++ b/Documentation/devicetree/bindings/usb/amlogic,dwc3.txt @@ -85,8 +85,8 @@ A child node must exist to represent the core DWC2 IP block. The name of the node is not important. The content of the node is defined in dwc2.txt. PHY documentation is provided in the following places: -- Documentation/devicetree/bindings/phy/meson-g12a-usb2-phy.txt -- Documentation/devicetree/bindings/phy/meson-g12a-usb3-pcie-phy.txt +- Documentation/devicetree/bindings/phy/amlogic,meson-g12a-usb2-phy.yaml +- Documentation/devicetree/bindings/phy/amlogic,meson-g12a-usb3-pcie-phy.yaml Example device nodes: usb: usb@ffe09000 { -- cgit From 3aa3c66aedef6a21ea1ad53f5b4491430ef0c84e Mon Sep 17 00:00:00 2001 From: Maxime Ripard Date: Wed, 2 Oct 2019 13:26:51 +0200 Subject: dt-bindings: usb: Bring back phy-names While the original bindings that were superseeded by the YAML schemas didn't mention that phy-names was needed, it turns out that phy-names is required if phys is set according to phy/phy-bindings.txt. Let's add back those properties. Fixes: 14ec072a19ad ("dt-bindings: usb: Convert USB HCD generic binding to YAML") Fixes: c93bcace1098 ("dt-bindings: usb: Convert the generic OHCI binding to YAML") Fixes: c3e2485d5f4f ("dt-bindings: usb: Convert the generic EHCI binding to YAML") Reported-by: Emmanuel Vadot Signed-off-by: Maxime Ripard Link: https://lore.kernel.org/r/20191002112651.100504-2-mripard@kernel.org Signed-off-by: Greg Kroah-Hartman --- Documentation/devicetree/bindings/usb/generic-ehci.yaml | 7 ++++++- Documentation/devicetree/bindings/usb/generic-ohci.yaml | 7 ++++++- Documentation/devicetree/bindings/usb/usb-hcd.yaml | 5 +++++ 3 files changed, 17 insertions(+), 2 deletions(-) (limited to 'Documentation') diff --git a/Documentation/devicetree/bindings/usb/generic-ehci.yaml b/Documentation/devicetree/bindings/usb/generic-ehci.yaml index 059f6ef1ad4a..1ca64c85191a 100644 --- a/Documentation/devicetree/bindings/usb/generic-ehci.yaml +++ b/Documentation/devicetree/bindings/usb/generic-ehci.yaml @@ -63,7 +63,11 @@ properties: description: Set this flag to force EHCI reset after resume. - phys: true + phys: + description: PHY specifier for the USB PHY + + phy-names: + const: usb required: - compatible @@ -89,6 +93,7 @@ examples: interrupts = <39>; clocks = <&ahb_gates 1>; phys = <&usbphy 1>; + phy-names = "usb"; }; ... diff --git a/Documentation/devicetree/bindings/usb/generic-ohci.yaml b/Documentation/devicetree/bindings/usb/generic-ohci.yaml index da5a14becbe5..bcffec1f1341 100644 --- a/Documentation/devicetree/bindings/usb/generic-ohci.yaml +++ b/Documentation/devicetree/bindings/usb/generic-ohci.yaml @@ -67,7 +67,11 @@ properties: description: Overrides the detected port count - phys: true + phys: + description: PHY specifier for the USB PHY + + phy-names: + const: usb required: - compatible @@ -84,6 +88,7 @@ examples: interrupts = <64>; clocks = <&usb_clk 6>, <&ahb_gates 2>; phys = <&usbphy 1>; + phy-names = "usb"; }; ... diff --git a/Documentation/devicetree/bindings/usb/usb-hcd.yaml b/Documentation/devicetree/bindings/usb/usb-hcd.yaml index 9c8c56d3a792..7263b7f2b510 100644 --- a/Documentation/devicetree/bindings/usb/usb-hcd.yaml +++ b/Documentation/devicetree/bindings/usb/usb-hcd.yaml @@ -18,8 +18,13 @@ properties: description: List of all the USB PHYs on this HCD + phy-names: + description: + Name specifier for the USB PHY + examples: - | usb { phys = <&usb2_phy1>, <&usb3_phy1>; + phy-names = "usb"; }; -- cgit From fc5f3782da3c73bbbe2293551219b2ded0660357 Mon Sep 17 00:00:00 2001 From: Biju Das Date: Tue, 17 Sep 2019 13:45:24 +0100 Subject: dt-bindings: serial: sh-sci: Document r8a774b1 bindings RZ/G2N (R8A774B1) SoC also has the R-Car Gen3 compatible SCIF and HSCIF ports, so document the SoC specific bindings. Signed-off-by: Biju Das Reviewed-by: Geert Uytterhoeven Acked-by: Rob Herring Link: https://lore.kernel.org/r/1568724324-26995-1-git-send-email-biju.das@bp.renesas.com Signed-off-by: Greg Kroah-Hartman --- Documentation/devicetree/bindings/serial/renesas,sci-serial.txt | 2 ++ 1 file changed, 2 insertions(+) (limited to 'Documentation') diff --git a/Documentation/devicetree/bindings/serial/renesas,sci-serial.txt b/Documentation/devicetree/bindings/serial/renesas,sci-serial.txt index dd63151dc8b6..b143d9a21b2d 100644 --- a/Documentation/devicetree/bindings/serial/renesas,sci-serial.txt +++ b/Documentation/devicetree/bindings/serial/renesas,sci-serial.txt @@ -26,6 +26,8 @@ Required properties: - "renesas,hscif-r8a77470" for R8A77470 (RZ/G1C) HSCIF compatible UART. - "renesas,scif-r8a774a1" for R8A774A1 (RZ/G2M) SCIF compatible UART. - "renesas,hscif-r8a774a1" for R8A774A1 (RZ/G2M) HSCIF compatible UART. + - "renesas,scif-r8a774b1" for R8A774B1 (RZ/G2N) SCIF compatible UART. + - "renesas,hscif-r8a774b1" for R8A774B1 (RZ/G2N) HSCIF compatible UART. - "renesas,scif-r8a774c0" for R8A774C0 (RZ/G2E) SCIF compatible UART. - "renesas,hscif-r8a774c0" for R8A774C0 (RZ/G2E) HSCIF compatible UART. - "renesas,scif-r8a7778" for R8A7778 (R-Car M1) SCIF compatible UART. -- cgit From 11c943a1a635d2c7141b5b6667ebb521ab4ecd58 Mon Sep 17 00:00:00 2001 From: Adam Zerella Date: Mon, 7 Oct 2019 13:36:57 +1100 Subject: hwmon: docs: Extend inspur-ipsps1 title underline Sphinx is generating a build warning as the title underline of this file is too short. Signed-off-by: Adam Zerella Reviewed-by: Jean Delvare Signed-off-by: Guenter Roeck --- Documentation/hwmon/inspur-ipsps1.rst | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'Documentation') diff --git a/Documentation/hwmon/inspur-ipsps1.rst b/Documentation/hwmon/inspur-ipsps1.rst index 2b871ae3448f..292c0c26bdd1 100644 --- a/Documentation/hwmon/inspur-ipsps1.rst +++ b/Documentation/hwmon/inspur-ipsps1.rst @@ -1,5 +1,5 @@ Kernel driver inspur-ipsps1 -======================= +=========================== Supported chips: -- cgit From c6875f3aacf2a5a913205accddabf0bfb75cac76 Mon Sep 17 00:00:00 2001 From: Boris Ostrovsky Date: Mon, 30 Sep 2019 16:44:41 -0400 Subject: x86/xen: Return from panic notifier Currently execution of panic() continues until Xen's panic notifier (xen_panic_event()) is called at which point we make a hypercall that never returns. This means that any notifier that is supposed to be called later as well as significant part of panic() code (such as pstore writes from kmsg_dump()) is never executed. There is no reason for xen_panic_event() to be this last point in execution since panic()'s emergency_restart() will call into xen_emergency_restart() from where we can perform our hypercall. Nevertheless, we will provide xen_legacy_crash boot option that will preserve original behavior during crash. This option could be used, for example, if running kernel dumper (which happens after panic notifiers) is undesirable. Reported-by: James Dingwall Signed-off-by: Boris Ostrovsky Reviewed-by: Juergen Gross --- Documentation/admin-guide/kernel-parameters.txt | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'Documentation') diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 4c1971960afa..5ea005c9e2d6 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -5267,6 +5267,10 @@ the unplug protocol never -- do not unplug even if version check succeeds + xen_legacy_crash [X86,XEN] + Crash from Xen panic notifier, without executing late + panic() code such as dumping handler. + xen_nopvspin [X86,XEN] Disables the ticketlock slowpath using Xen PV optimizations. -- cgit From 9783aa9917f8ae24759e67bf882f1aba32fe4ea1 Mon Sep 17 00:00:00 2001 From: Chris Down Date: Sun, 6 Oct 2019 17:58:32 -0700 Subject: mm, memcg: proportional memory.{low,min} reclaim cgroup v2 introduces two memory protection thresholds: memory.low (best-effort) and memory.min (hard protection). While they generally do what they say on the tin, there is a limitation in their implementation that makes them difficult to use effectively: that cliff behaviour often manifests when they become eligible for reclaim. This patch implements more intuitive and usable behaviour, where we gradually mount more reclaim pressure as cgroups further and further exceed their protection thresholds. This cliff edge behaviour happens because we only choose whether or not to reclaim based on whether the memcg is within its protection limits (see the use of mem_cgroup_protected in shrink_node), but we don't vary our reclaim behaviour based on this information. Imagine the following timeline, with the numbers the lruvec size in this zone: 1. memory.low=1000000, memory.current=999999. 0 pages may be scanned. 2. memory.low=1000000, memory.current=1000000. 0 pages may be scanned. 3. memory.low=1000000, memory.current=1000001. 1000001* pages may be scanned. (?!) * Of course, we won't usually scan all available pages in the zone even without this patch because of scan control priority, over-reclaim protection, etc. However, as shown by the tests at the end, these techniques don't sufficiently throttle such an extreme change in input, so cliff-like behaviour isn't really averted by their existence alone. Here's an example of how this plays out in practice. At Facebook, we are trying to protect various workloads from "system" software, like configuration management tools, metric collectors, etc (see this[0] case study). In order to find a suitable memory.low value, we start by determining the expected memory range within which the workload will be comfortable operating. This isn't an exact science -- memory usage deemed "comfortable" will vary over time due to user behaviour, differences in composition of work, etc, etc. As such we need to ballpark memory.low, but doing this is currently problematic: 1. If we end up setting it too low for the workload, it won't have *any* effect (see discussion above). The group will receive the full weight of reclaim and won't have any priority while competing with the less important system software, as if we had no memory.low configured at all. 2. Because of this behaviour, we end up erring on the side of setting it too high, such that the comfort range is reliably covered. However, protected memory is completely unavailable to the rest of the system, so we might cause undue memory and IO pressure there when we *know* we have some elasticity in the workload. 3. Even if we get the value totally right, smack in the middle of the comfort zone, we get extreme jumps between no pressure and full pressure that cause unpredictable pressure spikes in the workload due to the current binary reclaim behaviour. With this patch, we can set it to our ballpark estimation without too much worry. Any undesirable behaviour, such as too much or too little reclaim pressure on the workload or system will be proportional to how far our estimation is off. This means we can set memory.low much more conservatively and thus waste less resources *without* the risk of the workload falling off a cliff if we overshoot. As a more abstract technical description, this unintuitive behaviour results in having to give high-priority workloads a large protection buffer on top of their expected usage to function reliably, as otherwise we have abrupt periods of dramatically increased memory pressure which hamper performance. Having to set these thresholds so high wastes resources and generally works against the principle of work conservation. In addition, having proportional memory reclaim behaviour has other benefits. Most notably, before this patch it's basically mandatory to set memory.low to a higher than desirable value because otherwise as soon as you exceed memory.low, all protection is lost, and all pages are eligible to scan again. By contrast, having a gradual ramp in reclaim pressure means that you now still get some protection when thresholds are exceeded, which means that one can now be more comfortable setting memory.low to lower values without worrying that all protection will be lost. This is important because workingset size is really hard to know exactly, especially with variable workloads, so at least getting *some* protection if your workingset size grows larger than you expect increases user confidence in setting memory.low without a huge buffer on top being needed. Thanks a lot to Johannes Weiner and Tejun Heo for their advice and assistance in thinking about how to make this work better. In testing these changes, I intended to verify that: 1. Changes in page scanning become gradual and proportional instead of binary. To test this, I experimented stepping further and further down memory.low protection on a workload that floats around 19G workingset when under memory.low protection, watching page scan rates for the workload cgroup: +------------+-----------------+--------------------+--------------+ | memory.low | test (pgscan/s) | control (pgscan/s) | % of control | +------------+-----------------+--------------------+--------------+ | 21G | 0 | 0 | N/A | | 17G | 867 | 3799 | 23% | | 12G | 1203 | 3543 | 34% | | 8G | 2534 | 3979 | 64% | | 4G | 3980 | 4147 | 96% | | 0 | 3799 | 3980 | 95% | +------------+-----------------+--------------------+--------------+ As you can see, the test kernel (with a kernel containing this patch) ramps up page scanning significantly more gradually than the control kernel (without this patch). 2. More gradual ramp up in reclaim aggression doesn't result in premature OOMs. To test this, I wrote a script that slowly increments the number of pages held by stress(1)'s --vm-keep mode until a production system entered severe overall memory contention. This script runs in a highly protected slice taking up the majority of available system memory. Watching vmstat revealed that page scanning continued essentially nominally between test and control, without causing forward reclaim progress to become arrested. [0]: https://facebookmicrosites.github.io/cgroup2/docs/overview.html#case-study-the-fbtax2-project [akpm@linux-foundation.org: reflow block comments to fit in 80 cols] [chris@chrisdown.name: handle cgroup_disable=memory when getting memcg protection] Link: http://lkml.kernel.org/r/20190201045711.GA18302@chrisdown.name Link: http://lkml.kernel.org/r/20190124014455.GA6396@chrisdown.name Signed-off-by: Chris Down Acked-by: Johannes Weiner Reviewed-by: Roman Gushchin Cc: Michal Hocko Cc: Tejun Heo Cc: Dennis Zhou Cc: Tetsuo Handa Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/admin-guide/cgroup-v2.rst | 20 ++++++++++++++------ 1 file changed, 14 insertions(+), 6 deletions(-) (limited to 'Documentation') diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst index 0fa8c0e615c2..5361ebec3361 100644 --- a/Documentation/admin-guide/cgroup-v2.rst +++ b/Documentation/admin-guide/cgroup-v2.rst @@ -615,8 +615,8 @@ on an IO device and is an example of this type. Protections ----------- -A cgroup is protected to be allocated upto the configured amount of -the resource if the usages of all its ancestors are under their +A cgroup is protected upto the configured amount of the resource +as long as the usages of all its ancestors are under their protected levels. Protections can be hard guarantees or best effort soft boundaries. Protections can also be over-committed in which case only upto the amount available to the parent is protected among @@ -1096,7 +1096,10 @@ PAGE_SIZE multiple when read back. is within its effective min boundary, the cgroup's memory won't be reclaimed under any conditions. If there is no unprotected reclaimable memory available, OOM killer - is invoked. + is invoked. Above the effective min boundary (or + effective low boundary if it is higher), pages are reclaimed + proportionally to the overage, reducing reclaim pressure for + smaller overages. Effective min boundary is limited by memory.min values of all ancestor cgroups. If there is memory.min overcommitment @@ -1118,7 +1121,10 @@ PAGE_SIZE multiple when read back. Best-effort memory protection. If the memory usage of a cgroup is within its effective low boundary, the cgroup's memory won't be reclaimed unless memory can be reclaimed - from unprotected cgroups. + from unprotected cgroups. Above the effective low boundary (or + effective min boundary if it is higher), pages are reclaimed + proportionally to the overage, reducing reclaim pressure for + smaller overages. Effective low boundary is limited by memory.low values of all ancestor cgroups. If there is memory.low overcommitment @@ -2482,8 +2488,10 @@ system performance due to overreclaim, to the point where the feature becomes self-defeating. The memory.low boundary on the other hand is a top-down allocated -reserve. A cgroup enjoys reclaim protection when it's within its low, -which makes delegation of subtrees possible. +reserve. A cgroup enjoys reclaim protection when it's within its +effective low, which makes delegation of subtrees possible. It also +enjoys having reclaim pressure proportional to its overage when +above its effective low. The original high boundary, the hard limit, is defined as a strict limit that can not budge, even if the OOM killer has to be called. -- cgit From 59bb47985c1db229ccff8c5deebecd54fc77d2a9 Mon Sep 17 00:00:00 2001 From: Vlastimil Babka Date: Sun, 6 Oct 2019 17:58:45 -0700 Subject: mm, sl[aou]b: guarantee natural alignment for kmalloc(power-of-two) In most configurations, kmalloc() happens to return naturally aligned (i.e. aligned to the block size itself) blocks for power of two sizes. That means some kmalloc() users might unknowingly rely on that alignment, until stuff breaks when the kernel is built with e.g. CONFIG_SLUB_DEBUG or CONFIG_SLOB, and blocks stop being aligned. Then developers have to devise workaround such as own kmem caches with specified alignment [1], which is not always practical, as recently evidenced in [2]. The topic has been discussed at LSF/MM 2019 [3]. Adding a 'kmalloc_aligned()' variant would not help with code unknowingly relying on the implicit alignment. For slab implementations it would either require creating more kmalloc caches, or allocate a larger size and only give back part of it. That would be wasteful, especially with a generic alignment parameter (in contrast with a fixed alignment to size). Ideally we should provide to mm users what they need without difficult workarounds or own reimplementations, so let's make the kmalloc() alignment to size explicitly guaranteed for power-of-two sizes under all configurations. What this means for the three available allocators? * SLAB object layout happens to be mostly unchanged by the patch. The implicitly provided alignment could be compromised with CONFIG_DEBUG_SLAB due to redzoning, however SLAB disables redzoning for caches with alignment larger than unsigned long long. Practically on at least x86 this includes kmalloc caches as they use cache line alignment, which is larger than that. Still, this patch ensures alignment on all arches and cache sizes. * SLUB layout is also unchanged unless redzoning is enabled through CONFIG_SLUB_DEBUG and boot parameter for the particular kmalloc cache. With this patch, explicit alignment is guaranteed with redzoning as well. This will result in more memory being wasted, but that should be acceptable in a debugging scenario. * SLOB has no implicit alignment so this patch adds it explicitly for kmalloc(). The potential downside is increased fragmentation. While pathological allocation scenarios are certainly possible, in my testing, after booting a x86_64 kernel+userspace with virtme, around 16MB memory was consumed by slab pages both before and after the patch, with difference in the noise. [1] https://lore.kernel.org/linux-btrfs/c3157c8e8e0e7588312b40c853f65c02fe6c957a.1566399731.git.christophe.leroy@c-s.fr/ [2] https://lore.kernel.org/linux-fsdevel/20190225040904.5557-1-ming.lei@redhat.com/ [3] https://lwn.net/Articles/787740/ [akpm@linux-foundation.org: documentation fixlet, per Matthew] Link: http://lkml.kernel.org/r/20190826111627.7505-3-vbabka@suse.cz Signed-off-by: Vlastimil Babka Reviewed-by: Matthew Wilcox (Oracle) Acked-by: Michal Hocko Acked-by: Kirill A. Shutemov Acked-by: Christoph Hellwig Cc: David Sterba Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Ming Lei Cc: Dave Chinner Cc: "Darrick J . Wong" Cc: Christoph Hellwig Cc: James Bottomley Cc: Vlastimil Babka Cc: Joonsoo Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/core-api/memory-allocation.rst | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'Documentation') diff --git a/Documentation/core-api/memory-allocation.rst b/Documentation/core-api/memory-allocation.rst index 7744aa3bf2e0..939e3dfc86e9 100644 --- a/Documentation/core-api/memory-allocation.rst +++ b/Documentation/core-api/memory-allocation.rst @@ -98,6 +98,10 @@ limited. The actual limit depends on the hardware and the kernel configuration, but it is a good practice to use `kmalloc` for objects smaller than page size. +The address of a chunk allocated with `kmalloc` is aligned to at least +ARCH_KMALLOC_MINALIGN bytes. For sizes which are a power of two, the +alignment is also guaranteed to be at least the respective size. + For large allocations you can use :c:func:`vmalloc` and :c:func:`vzalloc`, or directly request pages from the page allocator. The memory allocated by `vmalloc` and related functions is -- cgit From fcfacb9f83745d9fa97937b8bc94a73bb0607912 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Tue, 8 Oct 2019 12:10:09 +0900 Subject: doc: move namespaces.rst from kbuild/ to core-api/ We discussed a better location for this file, and agreed that core-api/ is a good fit. Rename it to symbol-namespaces.rst for disambiguation, and also add it to index.rst and MAINTAINERS. Signed-off-by: Masahiro Yamada Acked-by: Matthias Maennich Signed-off-by: Jessica Yu --- Documentation/core-api/index.rst | 1 + Documentation/core-api/symbol-namespaces.rst | 154 +++++++++++++++++++++++++++ Documentation/kbuild/namespaces.rst | 154 --------------------------- 3 files changed, 155 insertions(+), 154 deletions(-) create mode 100644 Documentation/core-api/symbol-namespaces.rst delete mode 100644 Documentation/kbuild/namespaces.rst (limited to 'Documentation') diff --git a/Documentation/core-api/index.rst b/Documentation/core-api/index.rst index fa16a0538dcb..ab0eae1c153a 100644 --- a/Documentation/core-api/index.rst +++ b/Documentation/core-api/index.rst @@ -38,6 +38,7 @@ Core utilities protection-keys ../RCU/index gcc-plugins + symbol-namespaces Interfaces for kernel debugging diff --git a/Documentation/core-api/symbol-namespaces.rst b/Documentation/core-api/symbol-namespaces.rst new file mode 100644 index 000000000000..982ed7b568ac --- /dev/null +++ b/Documentation/core-api/symbol-namespaces.rst @@ -0,0 +1,154 @@ +================= +Symbol Namespaces +================= + +The following document describes how to use Symbol Namespaces to structure the +export surface of in-kernel symbols exported through the family of +EXPORT_SYMBOL() macros. + +.. Table of Contents + + === 1 Introduction + === 2 How to define Symbol Namespaces + --- 2.1 Using the EXPORT_SYMBOL macros + --- 2.2 Using the DEFAULT_SYMBOL_NAMESPACE define + === 3 How to use Symbols exported in Namespaces + === 4 Loading Modules that use namespaced Symbols + === 5 Automatically creating MODULE_IMPORT_NS statements + +1. Introduction +=============== + +Symbol Namespaces have been introduced as a means to structure the export +surface of the in-kernel API. It allows subsystem maintainers to partition +their exported symbols into separate namespaces. That is useful for +documentation purposes (think of the SUBSYSTEM_DEBUG namespace) as well as for +limiting the availability of a set of symbols for use in other parts of the +kernel. As of today, modules that make use of symbols exported into namespaces, +are required to import the namespace. Otherwise the kernel will, depending on +its configuration, reject loading the module or warn about a missing import. + +2. How to define Symbol Namespaces +================================== + +Symbols can be exported into namespace using different methods. All of them are +changing the way EXPORT_SYMBOL and friends are instrumented to create ksymtab +entries. + +2.1 Using the EXPORT_SYMBOL macros +================================== + +In addition to the macros EXPORT_SYMBOL() and EXPORT_SYMBOL_GPL(), that allow +exporting of kernel symbols to the kernel symbol table, variants of these are +available to export symbols into a certain namespace: EXPORT_SYMBOL_NS() and +EXPORT_SYMBOL_NS_GPL(). They take one additional argument: the namespace. +Please note that due to macro expansion that argument needs to be a +preprocessor symbol. E.g. to export the symbol `usb_stor_suspend` into the +namespace `USB_STORAGE`, use:: + + EXPORT_SYMBOL_NS(usb_stor_suspend, USB_STORAGE); + +The corresponding ksymtab entry struct `kernel_symbol` will have the member +`namespace` set accordingly. A symbol that is exported without a namespace will +refer to `NULL`. There is no default namespace if none is defined. `modpost` +and kernel/module.c make use the namespace at build time or module load time, +respectively. + +2.2 Using the DEFAULT_SYMBOL_NAMESPACE define +============================================= + +Defining namespaces for all symbols of a subsystem can be very verbose and may +become hard to maintain. Therefore a default define (DEFAULT_SYMBOL_NAMESPACE) +is been provided, that, if set, will become the default for all EXPORT_SYMBOL() +and EXPORT_SYMBOL_GPL() macro expansions that do not specify a namespace. + +There are multiple ways of specifying this define and it depends on the +subsystem and the maintainer's preference, which one to use. The first option +is to define the default namespace in the `Makefile` of the subsystem. E.g. to +export all symbols defined in usb-common into the namespace USB_COMMON, add a +line like this to drivers/usb/common/Makefile:: + + ccflags-y += -DDEFAULT_SYMBOL_NAMESPACE=USB_COMMON + +That will affect all EXPORT_SYMBOL() and EXPORT_SYMBOL_GPL() statements. A +symbol exported with EXPORT_SYMBOL_NS() while this definition is present, will +still be exported into the namespace that is passed as the namespace argument +as this argument has preference over a default symbol namespace. + +A second option to define the default namespace is directly in the compilation +unit as preprocessor statement. The above example would then read:: + + #undef DEFAULT_SYMBOL_NAMESPACE + #define DEFAULT_SYMBOL_NAMESPACE USB_COMMON + +within the corresponding compilation unit before any EXPORT_SYMBOL macro is +used. + +3. How to use Symbols exported in Namespaces +============================================ + +In order to use symbols that are exported into namespaces, kernel modules need +to explicitly import these namespaces. Otherwise the kernel might reject to +load the module. The module code is required to use the macro MODULE_IMPORT_NS +for the namespaces it uses symbols from. E.g. a module using the +usb_stor_suspend symbol from above, needs to import the namespace USB_STORAGE +using a statement like:: + + MODULE_IMPORT_NS(USB_STORAGE); + +This will create a `modinfo` tag in the module for each imported namespace. +This has the side effect, that the imported namespaces of a module can be +inspected with modinfo:: + + $ modinfo drivers/usb/storage/ums-karma.ko + [...] + import_ns: USB_STORAGE + [...] + + +It is advisable to add the MODULE_IMPORT_NS() statement close to other module +metadata definitions like MODULE_AUTHOR() or MODULE_LICENSE(). Refer to section +5. for a way to create missing import statements automatically. + +4. Loading Modules that use namespaced Symbols +============================================== + +At module loading time (e.g. `insmod`), the kernel will check each symbol +referenced from the module for its availability and whether the namespace it +might be exported to has been imported by the module. The default behaviour of +the kernel is to reject loading modules that don't specify sufficient imports. +An error will be logged and loading will be failed with EINVAL. In order to +allow loading of modules that don't satisfy this precondition, a configuration +option is available: Setting MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS=y will +enable loading regardless, but will emit a warning. + +5. Automatically creating MODULE_IMPORT_NS statements +===================================================== + +Missing namespaces imports can easily be detected at build time. In fact, +modpost will emit a warning if a module uses a symbol from a namespace +without importing it. +MODULE_IMPORT_NS() statements will usually be added at a definite location +(along with other module meta data). To make the life of module authors (and +subsystem maintainers) easier, a script and make target is available to fixup +missing imports. Fixing missing imports can be done with:: + + $ make nsdeps + +A typical scenario for module authors would be:: + + - write code that depends on a symbol from a not imported namespace + - `make` + - notice the warning of modpost telling about a missing import + - run `make nsdeps` to add the import to the correct code location + +For subsystem maintainers introducing a namespace, the steps are very similar. +Again, `make nsdeps` will eventually add the missing namespace imports for +in-tree modules:: + + - move or add symbols to a namespace (e.g. with EXPORT_SYMBOL_NS()) + - `make` (preferably with an allmodconfig to cover all in-kernel + modules) + - notice the warning of modpost telling about a missing import + - run `make nsdeps` to add the import to the correct code location + diff --git a/Documentation/kbuild/namespaces.rst b/Documentation/kbuild/namespaces.rst deleted file mode 100644 index 982ed7b568ac..000000000000 --- a/Documentation/kbuild/namespaces.rst +++ /dev/null @@ -1,154 +0,0 @@ -================= -Symbol Namespaces -================= - -The following document describes how to use Symbol Namespaces to structure the -export surface of in-kernel symbols exported through the family of -EXPORT_SYMBOL() macros. - -.. Table of Contents - - === 1 Introduction - === 2 How to define Symbol Namespaces - --- 2.1 Using the EXPORT_SYMBOL macros - --- 2.2 Using the DEFAULT_SYMBOL_NAMESPACE define - === 3 How to use Symbols exported in Namespaces - === 4 Loading Modules that use namespaced Symbols - === 5 Automatically creating MODULE_IMPORT_NS statements - -1. Introduction -=============== - -Symbol Namespaces have been introduced as a means to structure the export -surface of the in-kernel API. It allows subsystem maintainers to partition -their exported symbols into separate namespaces. That is useful for -documentation purposes (think of the SUBSYSTEM_DEBUG namespace) as well as for -limiting the availability of a set of symbols for use in other parts of the -kernel. As of today, modules that make use of symbols exported into namespaces, -are required to import the namespace. Otherwise the kernel will, depending on -its configuration, reject loading the module or warn about a missing import. - -2. How to define Symbol Namespaces -================================== - -Symbols can be exported into namespace using different methods. All of them are -changing the way EXPORT_SYMBOL and friends are instrumented to create ksymtab -entries. - -2.1 Using the EXPORT_SYMBOL macros -================================== - -In addition to the macros EXPORT_SYMBOL() and EXPORT_SYMBOL_GPL(), that allow -exporting of kernel symbols to the kernel symbol table, variants of these are -available to export symbols into a certain namespace: EXPORT_SYMBOL_NS() and -EXPORT_SYMBOL_NS_GPL(). They take one additional argument: the namespace. -Please note that due to macro expansion that argument needs to be a -preprocessor symbol. E.g. to export the symbol `usb_stor_suspend` into the -namespace `USB_STORAGE`, use:: - - EXPORT_SYMBOL_NS(usb_stor_suspend, USB_STORAGE); - -The corresponding ksymtab entry struct `kernel_symbol` will have the member -`namespace` set accordingly. A symbol that is exported without a namespace will -refer to `NULL`. There is no default namespace if none is defined. `modpost` -and kernel/module.c make use the namespace at build time or module load time, -respectively. - -2.2 Using the DEFAULT_SYMBOL_NAMESPACE define -============================================= - -Defining namespaces for all symbols of a subsystem can be very verbose and may -become hard to maintain. Therefore a default define (DEFAULT_SYMBOL_NAMESPACE) -is been provided, that, if set, will become the default for all EXPORT_SYMBOL() -and EXPORT_SYMBOL_GPL() macro expansions that do not specify a namespace. - -There are multiple ways of specifying this define and it depends on the -subsystem and the maintainer's preference, which one to use. The first option -is to define the default namespace in the `Makefile` of the subsystem. E.g. to -export all symbols defined in usb-common into the namespace USB_COMMON, add a -line like this to drivers/usb/common/Makefile:: - - ccflags-y += -DDEFAULT_SYMBOL_NAMESPACE=USB_COMMON - -That will affect all EXPORT_SYMBOL() and EXPORT_SYMBOL_GPL() statements. A -symbol exported with EXPORT_SYMBOL_NS() while this definition is present, will -still be exported into the namespace that is passed as the namespace argument -as this argument has preference over a default symbol namespace. - -A second option to define the default namespace is directly in the compilation -unit as preprocessor statement. The above example would then read:: - - #undef DEFAULT_SYMBOL_NAMESPACE - #define DEFAULT_SYMBOL_NAMESPACE USB_COMMON - -within the corresponding compilation unit before any EXPORT_SYMBOL macro is -used. - -3. How to use Symbols exported in Namespaces -============================================ - -In order to use symbols that are exported into namespaces, kernel modules need -to explicitly import these namespaces. Otherwise the kernel might reject to -load the module. The module code is required to use the macro MODULE_IMPORT_NS -for the namespaces it uses symbols from. E.g. a module using the -usb_stor_suspend symbol from above, needs to import the namespace USB_STORAGE -using a statement like:: - - MODULE_IMPORT_NS(USB_STORAGE); - -This will create a `modinfo` tag in the module for each imported namespace. -This has the side effect, that the imported namespaces of a module can be -inspected with modinfo:: - - $ modinfo drivers/usb/storage/ums-karma.ko - [...] - import_ns: USB_STORAGE - [...] - - -It is advisable to add the MODULE_IMPORT_NS() statement close to other module -metadata definitions like MODULE_AUTHOR() or MODULE_LICENSE(). Refer to section -5. for a way to create missing import statements automatically. - -4. Loading Modules that use namespaced Symbols -============================================== - -At module loading time (e.g. `insmod`), the kernel will check each symbol -referenced from the module for its availability and whether the namespace it -might be exported to has been imported by the module. The default behaviour of -the kernel is to reject loading modules that don't specify sufficient imports. -An error will be logged and loading will be failed with EINVAL. In order to -allow loading of modules that don't satisfy this precondition, a configuration -option is available: Setting MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS=y will -enable loading regardless, but will emit a warning. - -5. Automatically creating MODULE_IMPORT_NS statements -===================================================== - -Missing namespaces imports can easily be detected at build time. In fact, -modpost will emit a warning if a module uses a symbol from a namespace -without importing it. -MODULE_IMPORT_NS() statements will usually be added at a definite location -(along with other module meta data). To make the life of module authors (and -subsystem maintainers) easier, a script and make target is available to fixup -missing imports. Fixing missing imports can be done with:: - - $ make nsdeps - -A typical scenario for module authors would be:: - - - write code that depends on a symbol from a not imported namespace - - `make` - - notice the warning of modpost telling about a missing import - - run `make nsdeps` to add the import to the correct code location - -For subsystem maintainers introducing a namespace, the steps are very similar. -Again, `make nsdeps` will eventually add the missing namespace imports for -in-tree modules:: - - - move or add symbols to a namespace (e.g. with EXPORT_SYMBOL_NS()) - - `make` (preferably with an allmodconfig to cover all in-kernel - modules) - - notice the warning of modpost telling about a missing import - - run `make nsdeps` to add the import to the correct code location - -- cgit From b9918bdcac1ff7bf11f1ab64708267c73f9b2552 Mon Sep 17 00:00:00 2001 From: Joe Perches Date: Sat, 5 Oct 2019 09:46:43 -0700 Subject: Documentation/process: Add fallthrough pseudo-keyword Describe the fallthrough pseudo-keyword. Convert the coding-style.rst example to the keyword style. Add description and links to deprecated.rst. Miguel Ojeda comments on the eventual [[fallthrough]] syntax: "Note that C17/C18 does not have [[fallthrough]]. C++17 introduced it, as it is mentioned above. I would keep the __attribute__((fallthrough)) -> [[fallthrough]] change you did, though, since that is indeed the standard syntax (given the paragraph references C++17). I was told by Aaron Ballman (who is proposing them for C) that it is more or less likely that it becomes standardized in C2x. However, it is still not added to the draft (other attributes are already, though). See N2268 and N2269: http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2268.pdf (fallthrough) http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2269.pdf (attributes in general)" Signed-off-by: Joe Perches Acked-by: Nick Desaulniers Signed-off-by: Linus Torvalds --- Documentation/process/coding-style.rst | 2 +- Documentation/process/deprecated.rst | 33 +++++++++++++++++++++++---------- 2 files changed, 24 insertions(+), 11 deletions(-) (limited to 'Documentation') diff --git a/Documentation/process/coding-style.rst b/Documentation/process/coding-style.rst index f4a2198187f9..ada573b7d703 100644 --- a/Documentation/process/coding-style.rst +++ b/Documentation/process/coding-style.rst @@ -56,7 +56,7 @@ instead of ``double-indenting`` the ``case`` labels. E.g.: case 'K': case 'k': mem <<= 10; - /* fall through */ + fallthrough; default: break; } diff --git a/Documentation/process/deprecated.rst b/Documentation/process/deprecated.rst index 053b24a6dd38..179f2a5625a0 100644 --- a/Documentation/process/deprecated.rst +++ b/Documentation/process/deprecated.rst @@ -122,14 +122,27 @@ memory adjacent to the stack (when built without `CONFIG_VMAP_STACK=y`) Implicit switch case fall-through --------------------------------- -The C language allows switch cases to "fall through" when -a "break" statement is missing at the end of a case. This, -however, introduces ambiguity in the code, as it's not always -clear if the missing break is intentional or a bug. As there -have been a long list of flaws `due to missing "break" statements +The C language allows switch cases to "fall-through" when a "break" statement +is missing at the end of a case. This, however, introduces ambiguity in the +code, as it's not always clear if the missing break is intentional or a bug. + +As there have been a long list of flaws `due to missing "break" statements `_, we no longer allow -"implicit fall-through". In order to identify an intentional fall-through -case, we have adopted the marking used by static analyzers: a comment -saying `/* Fall through */`. Once the C++17 `__attribute__((fallthrough))` -is more widely handled by C compilers, static analyzers, and IDEs, we can -switch to using that instead. +"implicit fall-through". + +In order to identify intentional fall-through cases, we have adopted a +pseudo-keyword macro 'fallthrough' which expands to gcc's extension +__attribute__((__fallthrough__)). `Statement Attributes +`_ + +When the C17/C18 [[fallthrough]] syntax is more commonly supported by +C compilers, static analyzers, and IDEs, we can switch to using that syntax +for the macro pseudo-keyword. + +All switch/case blocks must end in one of: + + break; + fallthrough; + continue; + goto