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authorElena Reshetova <elena.reshetova@intel.com>2019-01-30 13:18:51 +0200
committerIngo Molnar <mingo@kernel.org>2019-02-04 09:03:31 +0100
commit47b8f3ab9c49daa824af848f9e02889662d8638f (patch)
treebd42ab897748eafaacdc5d0bb97256a678cee3d5 /arch/x86/include/asm
parent412f34a82ccf7dd52f6b197f6450a33f03342523 (diff)
downloadlinux-0-day-47b8f3ab9c49daa824af848f9e02889662d8638f.tar.gz
linux-0-day-47b8f3ab9c49daa824af848f9e02889662d8638f.tar.xz
refcount_t: Add ACQUIRE ordering on success for dec(sub)_and_test() variants
This adds an smp_acquire__after_ctrl_dep() barrier on successful decrease of refcounter value from 1 to 0 for refcount_dec(sub)_and_test variants and therefore gives stronger memory ordering guarantees than prior versions of these functions. Co-developed-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Elena Reshetova <elena.reshetova@intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Andrea Parri <andrea.parri@amarulasolutions.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Will Deacon <will.deacon@arm.com> Cc: dvyukov@google.com Cc: keescook@chromium.org Cc: stern@rowland.harvard.edu Link: https://lkml.kernel.org/r/1548847131-27854-2-git-send-email-elena.reshetova@intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/include/asm')
-rw-r--r--arch/x86/include/asm/refcount.h22
1 files changed, 18 insertions, 4 deletions
diff --git a/arch/x86/include/asm/refcount.h b/arch/x86/include/asm/refcount.h
index dbaed55c1c24..232f856e0db0 100644
--- a/arch/x86/include/asm/refcount.h
+++ b/arch/x86/include/asm/refcount.h
@@ -67,16 +67,30 @@ static __always_inline void refcount_dec(refcount_t *r)
static __always_inline __must_check
bool refcount_sub_and_test(unsigned int i, refcount_t *r)
{
- return GEN_BINARY_SUFFIXED_RMWcc(LOCK_PREFIX "subl",
+ bool ret = GEN_BINARY_SUFFIXED_RMWcc(LOCK_PREFIX "subl",
REFCOUNT_CHECK_LT_ZERO,
r->refs.counter, e, "er", i, "cx");
+
+ if (ret) {
+ smp_acquire__after_ctrl_dep();
+ return true;
+ }
+
+ return false;
}
static __always_inline __must_check bool refcount_dec_and_test(refcount_t *r)
{
- return GEN_UNARY_SUFFIXED_RMWcc(LOCK_PREFIX "decl",
- REFCOUNT_CHECK_LT_ZERO,
- r->refs.counter, e, "cx");
+ bool ret = GEN_UNARY_SUFFIXED_RMWcc(LOCK_PREFIX "decl",
+ REFCOUNT_CHECK_LT_ZERO,
+ r->refs.counter, e, "cx");
+
+ if (ret) {
+ smp_acquire__after_ctrl_dep();
+ return true;
+ }
+
+ return false;
}
static __always_inline __must_check