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* [glibc] Use relaxed atomics since there is no MO dependence
@ 2022-09-13 14:59 Wilco Dijkstra
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From: Wilco Dijkstra @ 2022-09-13 14:59 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=a30e960328fc60e066967d1224ecd5b6e173cda3
commit a30e960328fc60e066967d1224ecd5b6e173cda3
Author: Wilco Dijkstra <wdijkstr@arm.com>
Date: Tue Sep 13 11:58:07 2022 +0100
Use relaxed atomics since there is no MO dependence
Replace the 3 uses of atomic_bit_set and atomic_bit_test_set with
atomic_fetch_or_relaxed. Using relaxed MO is correct since the
atomics are used to ensure memory is released only once.
Reviewed-by: Florian Weimer <fweimer@redhat.com>
Diff:
---
nptl/nptl_free_tcb.c | 3 ++-
nptl/pthread_create.c | 2 +-
sysdeps/nptl/pthreadP.h | 8 +-------
3 files changed, 4 insertions(+), 9 deletions(-)
diff --git a/nptl/nptl_free_tcb.c b/nptl/nptl_free_tcb.c
index 0d31143ac8..86a8904898 100644
--- a/nptl/nptl_free_tcb.c
+++ b/nptl/nptl_free_tcb.c
@@ -24,7 +24,8 @@ void
__nptl_free_tcb (struct pthread *pd)
{
/* The thread is exiting now. */
- if (atomic_bit_test_set (&pd->cancelhandling, TERMINATED_BIT) == 0)
+ if ((atomic_fetch_or_relaxed (&pd->cancelhandling, TERMINATED_BITMASK)
+ & TERMINATED_BITMASK) == 0)
{
/* Free TPP data. */
if (pd->tpp != NULL)
diff --git a/nptl/pthread_create.c b/nptl/pthread_create.c
index e7e4ede6b2..ee29cb375d 100644
--- a/nptl/pthread_create.c
+++ b/nptl/pthread_create.c
@@ -487,7 +487,7 @@ start_thread (void *arg)
/* The thread is exiting now. Don't set this bit until after we've hit
the event-reporting breakpoint, so that td_thr_get_info on us while at
the breakpoint reports TD_THR_RUN state rather than TD_THR_ZOMBIE. */
- atomic_bit_set (&pd->cancelhandling, EXITING_BIT);
+ atomic_fetch_or_relaxed (&pd->cancelhandling, EXITING_BITMASK);
if (__glibc_unlikely (atomic_decrement_and_test (&__nptl_nthreads)))
/* This was the last thread. */
diff --git a/sysdeps/nptl/pthreadP.h b/sysdeps/nptl/pthreadP.h
index 39af275c25..c8521b0b23 100644
--- a/sysdeps/nptl/pthreadP.h
+++ b/sysdeps/nptl/pthreadP.h
@@ -43,12 +43,6 @@
atomic_compare_and_exchange_val_acq (&(descr)->member, new, old)
#endif
-#ifndef THREAD_ATOMIC_BIT_SET
-# define THREAD_ATOMIC_BIT_SET(descr, member, bit) \
- atomic_bit_set (&(descr)->member, bit)
-#endif
-
-
static inline short max_adaptive_count (void)
{
#if HAVE_TUNABLES
@@ -276,7 +270,7 @@ __do_cancel (void)
struct pthread *self = THREAD_SELF;
/* Make sure we get no more cancellations. */
- atomic_bit_set (&self->cancelhandling, EXITING_BIT);
+ atomic_fetch_or_relaxed (&self->cancelhandling, EXITING_BITMASK);
__pthread_unwind ((__pthread_unwind_buf_t *)
THREAD_GETMEM (self, cleanup_jmp_buf));
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2022-09-13 14:59 [glibc] Use relaxed atomics since there is no MO dependence Wilco Dijkstra
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