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2017-06-09drivers/fsi: expose direct-access slave APIJeremy Kerr
Allow drivers to access the slave address ranges. Signed-off-by: Jeremy Kerr <jk@ozlabs.org> Signed-off-by: Joel Stanley <joel@jms.id.au> Signed-off-by: Christopher Bostic <cbostic@linux.vnet.ibm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-06-09drivers/fsi: Add client driver register utilitiesChristopher Bostic
Add driver_register and driver_unregister wrappers for FSI. Signed-off-by: Christopher Bostic <cbostic@linux.vnet.ibm.com> Signed-off-by: Joel Stanley <joel@jms.id.au> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-06-09drivers/fsi: Add device read/write/peek APIJeremy Kerr
This change introduces the fsi device API: simple read, write and peek accessors for the devices' address spaces. Includes contributions from Christopher Bostic <cbostic@linux.vnet.ibm.com> and Edward A. James <eajames@us.ibm.com>. Signed-off-by: Edward A. James <eajames@us.ibm.com> Signed-off-by: Jeremy Kerr <jk@ozlabs.org> Signed-off-by: Christopher Bostic <cbostic@linux.vnet.ibm.com> Signed-off-by: Joel Stanley <joel@jms.id.au> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-06-09drivers/fsi: scan slaves & register devicesJeremy Kerr
Now that we have fsi_slave devices, scan each for endpoints, and register them on the fsi bus. Includes contributions from Christopher Bostic <cbostic@linux.vnet.ibm.com>. Signed-off-by: Jeremy Kerr <jk@ozlabs.org> Signed-off-by: Christopher Bostic <cbostic@linux.vnet.ibm.com> Signed-off-by: Joel Stanley <joel@jms.id.au> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-06-09lib: Add crc4 moduleJeremy Kerr
Add a little helper for crc4 calculations. This works 4-bits-at-a-time, using a simple table approach. We will need this in the FSI core code, as well as any master implementations that need to calculate CRCs in software. Signed-off-by: Jeremy Kerr <jk@ozlabs.org> Signed-off-by: Chris Bostic <cbostic@linux.vnet.ibm.com> Signed-off-by: Joel Stanley <joel@jms.id.au> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-06-09coresight: refactor with function of_coresight_get_cpuLeo Yan
This is refactor to add function of_coresight_get_cpu(), so it's used to retrieve CPU id for coresight component. Finally can use it as a common function for multiple places. Suggested-by: Mathieu Poirier <mathieu.poirier@linaro.org> Signed-off-by: Leo Yan <leo.yan@linaro.org> Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-06-09coresight: use const for device_node structuresLeo Yan
Almost low level functions from open firmware have used const to qualify device_node structures, so add const for device_node parameters in of_coresight related functions. Signed-off-by: Leo Yan <leo.yan@linaro.org> Reviewed-by: Stephen Boyd <sboyd@codeaurora.org> Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-06-09sh: superhyway: use dev_groups and not dev_attrs for bus_typeGreg Kroah-Hartman
The dev_attrs field has long been "depreciated" and is finally being removed, so move the driver to use the "correct" dev_groups field instead for struct bus_type. Cc: Yoshinori Sato <ysato@users.sourceforge.jp> Cc: Rich Felker <dalias@libc.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: <linux-sh@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-06-09driver core: remove class_attrs from struct classGreg Kroah-Hartman
This field is no longer used or needed (use class_groups instead), so it can be removed along with the driver core functionality that created and removed these files. Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-06-09Merge branch 'rcu/urgent' of ↵Ingo Molnar
git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into rcu/urgent Pull RCU fix from Paul E. McKenney: " This series enables srcu_read_lock() and srcu_read_unlock() to be used from interrupt handlers, which fixes a bug in KVM's use of SRCU in delivery of interrupts to guest OSes. " Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-06-09KEYS: sanitize key structs before freeingEric Biggers
While a 'struct key' itself normally does not contain sensitive information, Documentation/security/keys.txt actually encourages this: "Having a payload is not required; and the payload can, in fact, just be a value stored in the struct key itself." In case someone has taken this advice, or will take this advice in the future, zero the key structure before freeing it. We might as well, and as a bonus this could make it a bit more difficult for an adversary to determine which keys have recently been in use. This is safe because the key_jar cache does not use a constructor. Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: James Morris <james.l.morris@oracle.com>
2017-06-08srcu: Remove Classic SRCUPaul E. McKenney
Classic SRCU was only ever intended to be a fallback in case of issues with Tree/Tiny SRCU, and the latter two are doing quite well in testing. This commit therefore removes Classic SRCU. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-06-08rcu: Remove SPARSE_RCU_POINTER Kconfig optionPaul E. McKenney
The sparse-based checking for non-RCU accesses to RCU-protected pointers has been around for a very long time, and it is now the only type of sparse-based checking that is optional. This commit therefore makes it unconditional. Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Fengguang Wu <fengguang.wu@intel.com>
2017-06-08rcu: Remove #ifdef moving rcu_end_inkernel_boot from rcupdate.hPaul E. McKenney
This commit removes a #ifdef and saves a few lines of code by moving the rcu_end_inkernel_boot() function from include/linux/rcupdate.h to include/linux/rcutiny.h (for TINY_RCU) and to include/linux/rcutree.h (for TREE_RCU). Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-06-08rcu: Remove nohz_full full-system-idle state machinePaul E. McKenney
The NO_HZ_FULL_SYSIDLE full-system-idle capability was added in 2013 by commit 0edd1b1784cb ("nohz_full: Add full-system-idle state machine"), but has not been used. This commit therefore removes it. If it turns out to be needed later, this commit can always be reverted. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Rik van Riel <riel@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-06-08srcu: Use rnp->lock wrappers to replace explicit memory barriersPaul E. McKenney
This commit uses TREE RCU's rnp->lock wrappers to replace a few explicit memory barriers. This change also has the advantage of making SRCU's memory-ordering properties be implemented in roughly the same way as they are in Tree RCU. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-06-08rcu: Refactor #includes from include/linux/rcupdate.hPaul E. McKenney
The list of #includes from include/linux/rcupdate.h has grown quite a bit, so it is time to trim it. This commit moves the #include of include/linux/ktime.h to include/linux/rcutiny.h, along with the Tiny-RCU-only function that was the only thing needing ktimem.h. It then reconstructs the files included into include/linux/ktime.h based on what is actually needed, with significant help from the 0day Test Robot. This single change reduces the .i file footprint from rcupdate.h from 9018 lines to 7101 lines. Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-06-08bcm47xx: Fix build regressionArnd Bergmann
Commit 0bc2d534708b ("rcu: Refactor #includes from include/linux/rcupdate.h") caused a build regression in an MTD partition driver: In file included from drivers/mtd/bcm47xxpart.c:12:0: include/linux/bcm47xx_nvram.h: In function 'bcm47xx_nvram_init_from_mem': include/linux/bcm47xx_nvram.h:27:10: error: 'ENOTSUPP' undeclared (first use in this function) The rcupdate.h file has no particular need for linux/errno.h, so this commit includes linux/errno.h into bcm47xx_nvram.h. Fixes: 0bc2d534708b ("rcu: Refactor #includes from include/linux/rcupdate.h") Signed-off-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-06-08srcu: Apply trivial callback lists to shrink Tiny SRCUPaul E. McKenney
The rcu_segcblist structure provides quite a bit of functionality, and Tiny SRCU needs almost none of it. So this commit replaces Tiny SRCU's uses of rcu_segcblist with a simple singly linked list with tail pointer. This change significantly reduces Tiny SRCU's memory footprint, more than making up for the growth caused by the creation of rcu_segcblist.c Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-06-08srcu: Shrink srcu.h by moving docbook and private functionPaul E. McKenney
The call_srcu() docbook entry is currently in include/linux/srcu.h, which causes needless processing for each include point. This commit therefore moves this entry to kernel/rcu/srcutree.c, which the compiler reads only once. In addition, the srcu_batches_completed() function is used only within RCU and its torture-test suites. This commit therefore also moves this function's declaration from include/linux/srcutiny.h, include/linux/srcutree.h, and include/linux/srcuclassic.h to kernel/rcu/rcu.h. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-06-08rcu: Move rcutiny.h to new empty/true/false-function stylePaul E. McKenney
This commit saves a few lines in include/linux/rcutiny.h by moving to single-line definitions for empty functions, instead of the old style where the two curly braces each get their own line. Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-06-08rcu: Move rcu_request_urgent_qs_task() out of rcutiny.h and rcutree.hPaul E. McKenney
The rcu_request_urgent_qs_task() function is used only within RCU, so there is no point in exporting it to the rest of the kernel from nclude/linux/rcutiny.h and include/linux/rcutree.h. This commit therefore moves this function to kernel/rcu/rcu.h. Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-06-08rcu: Move torture-related functions out of rcutiny.h and rcutree.hPaul E. McKenney
The various functions similar to rcu_batches_started(), the function show_rcu_gp_kthreads(), the various functions similar to rcu_force_quiescent_state(), and the variables rcutorture_testseq and rcutorture_vernum are used only within RCU. There is therefore no point in exporting them to the kernel at large from include/linux/rcutiny.h and include/linux/rcutree.h. This commit therefore moves all of these to kernel/rcu/rcu.h. Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-06-08rcu: move rcupdate.h to the new true/false-function stylePaul E. McKenney
This commit saves a few lines in include/linux/rcupdate.h by moving to single-line definitions for functions that just return either true or false, instead of the old style where the two curly braces each get their own line. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-06-08rcu: Move rcu_ftrace_dump() from rcupdate.h to rcu.hPaul E. McKenney
The rcu_ftrace_dump() function is used only internally to RCU. This commit therefore moves its declaration from include/linux/rcupdate.h to kernel/rcu/rcu.h. Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-06-08rcu: Move rcu_is_nocb_cpu() from rcupdate.h to rcu.hPaul E. McKenney
The rcu_is_nocb_cpu() function is used only internally to RCU. This commit therefore moves its declaration from include/linux/rcupdate.h to kernel/rcu/rcu.h. Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-06-08rcu: Remove linux/debugobjects.h from rcupdate.hPaul E. McKenney
The include/linux/rcupdate.h file does not actually need anything from linux/debugobjects.h, so this commit removes the inclusion. Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-06-08rcu: Move the RCU_SCHEDULER_ definitions from rcupdate.hPaul E. McKenney
The RCU_SCHEDULER_INACTIVE, RCU_SCHEDULER_INIT, and RCU_SCHEDULER_RUNNING definitions are used only within RCU, so this commit moves them from include/linux/rcupdate.h to kernel/rcu/rcu.h. Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-06-08rcu: Eliminate the unused __rcu_is_watching() functionPaul E. McKenney
The __rcu_is_watching() function is currently not used, aside from to implement the rcu_is_watching() function. This commit therefore eliminates __rcu_is_watching(), which has the beneficial side-effect of shrinking include/linux/rcupdate.h a bit. Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-06-08rcu: Move rcupdate.h to new empty-function stylePaul E. McKenney
This commit saves a few lines in include/linux/rcupdate.h by moving to single-line definitions for empty functions, instead of the old style where the two curly braces each get their own line. Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-06-08rcu: Remove UINT_CMP_GE() and UINT_CMP_LT()Paul E. McKenney
The UINT_CMP_GE() and UINT_CMP_LT() macros are not used, so this commit removes them. Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-06-08rcu: Move torture-related definitions from rcupdate.h to rcu.hPaul E. McKenney
The include/linux/rcupdate.h file contains a number of definitions that are used only to communicate between rcutorture, rcuperf, and the RCU code itself. There is no point in having these definitions exposed globally throughout the kernel, so this commit moves them to kernel/rcu/rcu.h. This change has the added benefit of shrinking rcupdate.h. Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-06-08rcu: Move expediting-related access/control out of rcupdate.hPaul E. McKenney
The rcu_gp_is_normal(), rcu_gp_is_expedited(), rcu_expedite_gp(), and rcu_unexpedite_gp() functions are intended only for use within the RCU implementation itself -- the sysfs access is what should be used outside of RCU. This commit therefore moves the declarations for these functions to kernel/rcu/rcu.h, and also includes this file into kernel/rcu/rcutorture.c and kernel/rcu/rcuperf.c. This also has the beneficial effect of shrinking rcupdate.c a bit. Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-06-08rcu: Move rcu_expedited and rcu_normal externs from rcupdate.hPaul E. McKenney
The rcu_expedited and rcu_normal variables are used only by sysctl and kernel/rcu/update.c, so it does not make sense to their extern declarations in rcupdate.h. This commit therefore moves these extern declarations to update.c. Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-06-08rcu: Move docbook comments out of rcupdate.hPaul E. McKenney
The include/linux/rcupdate.h file is included by more than 200 files, so shrinking it should provide some build-time benefits. This commit therefore moves several docbook comments from rcupdate.h to kernel/rcu/update.c, kernel/rcu/tree.c, and kernel/rcu/tree_plugin.h, thus reducing the number of times that the compiler has to scan these comments. This likely provides only a small benefit, but every little bit helps. This commit also fixes a malformed bulleted list noted by the 0day Test Robot. Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-06-08rcu: Flag need for rcu_node_tree.h and rcu_segcblist.h visibilityPaul E. McKenney
The rcu_node_tree.h and rcu_segcblist.h header files in the include/linux directory might appear at first sight to be internal to the RCU implementation. However, the definitions in these files are needed to determine the size of TREE SRCU's srcu_struct structure, so they must be externally visible, which is why they live in include/linux. This commit adds comments to this effect to those files. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-06-08Merge tag 'pm-4.12-rc5' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm Pull power management fixes from Rafael Wysocki: "These revert one problematic commit related to system sleep and fix one recent intel_pstate regression. Specifics: - Revert a recent commit that attempted to avoid spurious wakeups from suspend-to-idle via ACPI SCI, but introduced regressions on some systems (Rafael Wysocki). We will get back to the problem it tried to address in the next cycle. - Fix a possible division by 0 during intel_pstate initialization due to a missing check (Rafael Wysocki)" * tag 'pm-4.12-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm: Revert "ACPI / sleep: Ignore spurious SCI wakeups from suspend-to-idle" cpufreq: intel_pstate: Avoid division by 0 in min_perf_pct_min()
2017-06-09Merge branches 'intel_pstate' and 'pm-sleep'Rafael J. Wysocki
* intel_pstate: cpufreq: intel_pstate: Avoid division by 0 in min_perf_pct_min() * pm-sleep: Revert "ACPI / sleep: Ignore spurious SCI wakeups from suspend-to-idle"
2017-06-08securityfs: add the ability to support symlinksJohn Johansen
Signed-off-by: John Johansen <john.johansen@canonical.com> Reviewed-by: Seth Arnold <seth.arnold@canonical.com> Acked-by: Kees Cook <keescook@chromium.org>
2017-06-08Merge branch 'psy-reboot-mode-immutable' into psy-nextSebastian Reichel
2017-06-08power: reset: reboot-mode: Make include file globalBjorn Andersson
Move the reboot-mode.h include file into include/linux to allow drivers outside drivers/power/reset to implement reboot-mode. Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org> Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
2017-06-08power: supply: bq27xxx: Add power_supply_battery_info supportLiam Breck
Previously there was no way to configure these chips in the event that the defaults didn't match the battery in question. For chips with RAM data memory (and also those with flash/NVM data memory if CONFIG_BATTERY_BQ27XXX_DT_UPDATES_NVM is defined and the user has not set module param dt_monitored_battery_updates_nvm=0) we now call power_supply_get_battery_info(), check its values, and write battery properties to chip data memory if there is a dm_regs table for the chip. Signed-off-by: Matt Ranostay <matt@ranostay.consulting> Signed-off-by: Liam Breck <kernel@networkimprov.net> Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
2017-06-08power: supply: bq27xxx: Add chip data memory read/write supportLiam Breck
Add these to enable read/write of chip data memory RAM/NVM/flash: bq27xxx_battery_seal() bq27xxx_battery_unseal() bq27xxx_battery_set_cfgupdate() bq27xxx_battery_soft_reset() bq27xxx_battery_read_dm_block() bq27xxx_battery_write_dm_block() bq27xxx_battery_checksum_dm_block() Signed-off-by: Matt Ranostay <matt@ranostay.consulting> Signed-off-by: Liam Breck <kernel@networkimprov.net> Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
2017-06-08Merge tag 'rxrpc-rewrite-20170607-v2' of ↵David S. Miller
git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs David Howells says: ==================== rxrpc: Tx length parameter Here's a set of patches that allows someone initiating a client call with AF_RXRPC to indicate upfront the total amount of data that will be transmitted. This will allow AF_RXRPC to encrypt directly from source buffer to packet rather than having to copy into the buffer and only encrypt when it's full (the encrypted portion of the packet starts with a length and so we can't encrypt until we know what the length will be). The three patches are: (1) Provide a means of finding out what control message types are actually supported. EINVAL is reported if an unsupported cmsg type is seen, so we don't want to set the new cmsg unless we know it will be accepted. (2) Consolidate some stuff into a struct to reduce the parameter count on the function that parses the cmsg buffer. (3) Introduce the RXRPC_TX_LENGTH cmsg. This can be provided on the first sendmsg() that contributes data to a client call request or a service call reply. If provided, the user must provide exactly that amount of data or an error will be incurred. Changes in version 2: (*) struct rxrpc_send_params::tx_total_len should be s64 not u64. Thanks to Julia Lawall for reporting this. ==================== Signed-off-by: David S. Miller <davem@davemloft.net>
2017-06-08srcu: Shrink Tiny SRCU a bitPaul E. McKenney
In Tiny SRCU, __srcu_read_lock() is a trivial function, outweighed by its EXPORT_SYMBOL_GPL(), and on many architectures, its call sequence. This commit therefore moves it to srcutiny.h so that it can be inlined. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-06-08srcu: Make SRCU be once again optionalPaul E. McKenney
Commit d160a727c40e ("srcu: Make SRCU be built by default") in response to build errors, which were caused by code that included srcu.h despite !SRCU. However, srcutiny.o is almost 2K of code, which is not insignificant for those attempting to run the Linux kernel on IoT devices. This commit therefore makes SRCU be once again optional, and adjusts srcu.h to allow error-free inclusion in !SRCU kernel builds. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by: Nicolas Pitre <nico@linaro.org>
2017-06-08rcu: Print out rcupdate.c non-default boot-time settingsPaul E. McKenney
This commit adds a rcupdate_announce_bootup_oddness() function to print out non-default values of significant kernel boot parameter settings to aid in debugging. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-06-08srcu: Shrink Tiny SRCU a bit morePaul E. McKenney
This commit rearranges Tiny SRCU's srcu_struct structure, substitutes u8 for bool, and shrinks counters down to short. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-06-08atomics: Add header comment so spin_unlock_wait()Paul E. McKenney
There is material describing the ordering guarantees provided by spin_unlock_wait(), but it is not necessarily easy to find. This commit therefore adds a docbook header comment to this function informally describing its semantics. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by: Peter Zijlstra <peterz@infradead.org>
2017-06-08srcu: Allow use of Classic SRCU from both process and interrupt contextPaolo Bonzini
Linu Cherian reported a WARN in cleanup_srcu_struct() when shutting down a guest running iperf on a VFIO assigned device. This happens because irqfd_wakeup() calls srcu_read_lock(&kvm->irq_srcu) in interrupt context, while a worker thread does the same inside kvm_set_irq(). If the interrupt happens while the worker thread is executing __srcu_read_lock(), updates to the Classic SRCU ->lock_count[] field or the Tree SRCU ->srcu_lock_count[] field can be lost. The docs say you are not supposed to call srcu_read_lock() and srcu_read_unlock() from irq context, but KVM interrupt injection happens from (host) interrupt context and it would be nice if SRCU supported the use case. KVM is using SRCU here not really for the "sleepable" part, but rather due to its IPI-free fast detection of grace periods. It is therefore not desirable to switch back to RCU, which would effectively revert commit 719d93cd5f5c ("kvm/irqchip: Speed up KVM_SET_GSI_ROUTING", 2014-01-16). However, the docs are overly conservative. You can have an SRCU instance only has users in irq context, and you can mix process and irq context as long as process context users disable interrupts. In addition, __srcu_read_unlock() actually uses this_cpu_dec() on both Tree SRCU and Classic SRCU. For those two implementations, only srcu_read_lock() is unsafe. When Classic SRCU's __srcu_read_unlock() was changed to use this_cpu_dec(), in commit 5a41344a3d83 ("srcu: Simplify __srcu_read_unlock() via this_cpu_dec()", 2012-11-29), __srcu_read_lock() did two increments. Therefore it kept __this_cpu_inc(), with preempt_disable/enable in the caller. Tree SRCU however only does one increment, so on most architectures it is more efficient for __srcu_read_lock() to use this_cpu_inc(), and any performance differences appear to be down in the noise. Cc: stable@vger.kernel.org Fixes: 719d93cd5f5c ("kvm/irqchip: Speed up KVM_SET_GSI_ROUTING") Reported-by: Linu Cherian <linuc.decode@gmail.com> Suggested-by: Linu Cherian <linuc.decode@gmail.com> Cc: kvm@vger.kernel.org Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>