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| author | Will Deacon <will.deacon@arm.com> | 2014-02-07 19:12:32 +0100 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2014-04-02 00:58:50 +0100 |
| commit | 8c8e77aa65fd685e09804e7a6709c82baa3648d1 (patch) | |
| tree | af670d70c84d61eac69afadf009c26e8a89fa58f /arch | |
| parent | b768f21422c7ba677c3a2e594881fd412984e665 (diff) | |
| download | lwn-8c8e77aa65fd685e09804e7a6709c82baa3648d1.tar.gz lwn-8c8e77aa65fd685e09804e7a6709c82baa3648d1.zip | |
ARM: 7955/1: spinlock: ensure we have a compiler barrier before sev
commit 7c8746a9eb287642deaad0e7c2cdf482dce5e4be upstream.
When unlocking a spinlock, we require the following, strictly ordered
sequence of events:
<barrier> /* dmb */
<unlock>
<barrier> /* dsb */
<sev>
Whilst the code does indeed reflect this in terms of the architecture,
the final <barrier> + <sev> have been contracted into a single inline
asm without a "memory" clobber, therefore the compiler is at liberty to
reorder the unlock to the end of the above sequence. In such a case,
a waiting CPU may be woken up before the lock has been unlocked, leading
to extremely poor performance.
This patch reworks the dsb_sev() function to make use of the dsb()
macro and ensure ordering against the unlock.
Reported-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
[bwh: Backported to 3.2: 'ishst' variant is not used here]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/arm/include/asm/spinlock.h | 15 |
1 files changed, 3 insertions, 12 deletions
diff --git a/arch/arm/include/asm/spinlock.h b/arch/arm/include/asm/spinlock.h index 65fa3c88095c..095a9a3f40b4 100644 --- a/arch/arm/include/asm/spinlock.h +++ b/arch/arm/include/asm/spinlock.h @@ -44,18 +44,9 @@ static inline void dsb_sev(void) { -#if __LINUX_ARM_ARCH__ >= 7 - __asm__ __volatile__ ( - "dsb\n" - SEV - ); -#else - __asm__ __volatile__ ( - "mcr p15, 0, %0, c7, c10, 4\n" - SEV - : : "r" (0) - ); -#endif + + dsb(); + __asm__(SEV); } /* |