Messages in this thread | | | Subject | Re: [PATCH] [bugfix] replace unnessary ldax with common ldr | From | Vladimir Murzin <> | Date | Wed, 31 Aug 2016 14:30:40 +0100 |
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On 30/08/16 10:07, Catalin Marinas wrote: > On Tue, Aug 30, 2016 at 02:35:31PM +0800, Kenneth Lee wrote: >> (add comment for the previous mail, sorry for the duplication) >> >> There is no store_ex pairing with this load_ex. It is not necessary and >> gave wrong hint to the cache system. >> >> Signed-off-by: Kenneth Lee <liguozhu@hisilicon.com> >> --- >> arch/arm64/include/asm/spinlock.h | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/arch/arm64/include/asm/spinlock.h b/arch/arm64/include/asm/spinlock.h >> index c85e96d..3334c4f 100644 >> --- a/arch/arm64/include/asm/spinlock.h >> +++ b/arch/arm64/include/asm/spinlock.h >> @@ -63,7 +63,7 @@ static inline void arch_spin_lock(arch_spinlock_t *lock) >> */ >> " sevl\n" >> "2: wfe\n" >> -" ldaxrh %w2, %4\n" >> +" ldrh %w2, %4\n" >> " eor %w1, %w2, %w0, lsr #16\n" >> " cbnz %w1, 2b\n" >> /* We got the lock. Critical section starts here. */ > > This is needed because the arch_spin_unlock() code only uses an STLR > without an explicit SEV (like we have on AArch32). An event is > automatically generated when the exclusive monitor is cleared by STLR. > But without setting it with a load exclusive in arch_spin_lock() (even > though it does not acquire the lock), there won't be anything to clear, > hence no event to be generated. In this case, the WFE would wait > indefinitely. >
Maybe worth to add this as a comment, no?
Cheers Vladimir
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