Messages in this thread | | | Date | Thu, 1 Sep 2016 11:20:07 +0100 | From | Catalin Marinas <> | Subject | Re: [PATCH] [bugfix] replace unnessary ldax with common ldr |
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On Wed, Aug 31, 2016 at 02:30:40PM +0100, Vladimir Murzin wrote: > 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?
Yes, we just need to find someone to send a patch ;).
-- Catalin
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