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author | Mauro Carvalho Chehab <mchehab+samsung@kernel.org> | 2019-02-18 10:12:12 -0500 |
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committer | Mauro Carvalho Chehab <mchehab+samsung@kernel.org> | 2019-02-18 10:12:12 -0500 |
commit | 5f09bc8cc4010a3ea17c5881a62fc45192ebe7b0 (patch) | |
tree | c8e30ba4eaf357699ef97a786bf56661f4591be8 /arch/mips/include/asm/barrier.h | |
parent | 6fd369dd1cb65a032f1ab9227033ecb7b759656d (diff) | |
parent | a3b22b9f11d9fbc48b0291ea92259a5a810e9438 (diff) |
Merge tag 'v5.0-rc7' into patchwork
Linux 5.0-rc7
* tag 'v5.0-rc7': (1667 commits)
Linux 5.0-rc7
Input: elan_i2c - add ACPI ID for touchpad in Lenovo V330-15ISK
Input: st-keyscan - fix potential zalloc NULL dereference
Input: apanel - switch to using brightness_set_blocking()
powerpc/64s: Fix possible corruption on big endian due to pgd/pud_present()
efi/arm: Revert "Defer persistent reservations until after paging_init()"
arm64, mm, efi: Account for GICv3 LPI tables in static memblock reserve table
sunrpc: fix 4 more call sites that were using stack memory with a scatterlist
include/linux/module.h: copy __init/__exit attrs to init/cleanup_module
Compiler Attributes: add support for __copy (gcc >= 9)
lib/crc32.c: mark crc32_le_base/__crc32c_le_base aliases as __pure
auxdisplay: ht16k33: fix potential user-after-free on module unload
x86/platform/UV: Use efi_runtime_lock to serialise BIOS calls
i2c: bcm2835: Clear current buffer pointers and counts after a transfer
i2c: cadence: Fix the hold bit setting
drm: Use array_size() when creating lease
dm thin: fix bug where bio that overwrites thin block ignores FUA
Revert "exec: load_script: don't blindly truncate shebang string"
Revert "gfs2: read journal in large chunks to locate the head"
net: ethernet: freescale: set FEC ethtool regs version
...
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Diffstat (limited to 'arch/mips/include/asm/barrier.h')
-rw-r--r-- | arch/mips/include/asm/barrier.h | 36 |
1 files changed, 36 insertions, 0 deletions
diff --git a/arch/mips/include/asm/barrier.h b/arch/mips/include/asm/barrier.h index a5eb1bb199a7..b7f6ac5e513c 100644 --- a/arch/mips/include/asm/barrier.h +++ b/arch/mips/include/asm/barrier.h @@ -222,6 +222,42 @@ #define __smp_mb__before_atomic() __smp_mb__before_llsc() #define __smp_mb__after_atomic() smp_llsc_mb() +/* + * Some Loongson 3 CPUs have a bug wherein execution of a memory access (load, + * store or pref) in between an ll & sc can cause the sc instruction to + * erroneously succeed, breaking atomicity. Whilst it's unusual to write code + * containing such sequences, this bug bites harder than we might otherwise + * expect due to reordering & speculation: + * + * 1) A memory access appearing prior to the ll in program order may actually + * be executed after the ll - this is the reordering case. + * + * In order to avoid this we need to place a memory barrier (ie. a sync + * instruction) prior to every ll instruction, in between it & any earlier + * memory access instructions. Many of these cases are already covered by + * smp_mb__before_llsc() but for the remaining cases, typically ones in + * which multiple CPUs may operate on a memory location but ordering is not + * usually guaranteed, we use loongson_llsc_mb() below. + * + * This reordering case is fixed by 3A R2 CPUs, ie. 3A2000 models and later. + * + * 2) If a conditional branch exists between an ll & sc with a target outside + * of the ll-sc loop, for example an exit upon value mismatch in cmpxchg() + * or similar, then misprediction of the branch may allow speculative + * execution of memory accesses from outside of the ll-sc loop. + * + * In order to avoid this we need a memory barrier (ie. a sync instruction) + * at each affected branch target, for which we also use loongson_llsc_mb() + * defined below. + * + * This case affects all current Loongson 3 CPUs. + */ +#ifdef CONFIG_CPU_LOONGSON3_WORKAROUNDS /* Loongson-3's LLSC workaround */ +#define loongson_llsc_mb() __asm__ __volatile__(__WEAK_LLSC_MB : : :"memory") +#else +#define loongson_llsc_mb() do { } while (0) +#endif + #include <asm-generic/barrier.h> #endif /* __ASM_BARRIER_H */ |