From: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
To: 'GNU C Library' <libc-alpha@sourceware.org>
Cc: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Subject: [PATCH] Use C11 atomics instead of atomic_increment(_val)
Date: Thu, 8 Sep 2022 14:01:55 +0000 [thread overview]
Message-ID: <AS4PR08MB790126C706EFA1DCC038BE6183409@AS4PR08MB7901.eurprd08.prod.outlook.com> (raw)
Replace atomic_increment and atomic_increment_val with atomic_fetch_add_relaxed.
One case in sem_post.c uses release semantics (see comment above it).
Passes regress on AArch64.
---
diff --git a/htl/pt-create.c b/htl/pt-create.c
index ce52ed9f52210a4e4c7a049ebee817ec9ccfeeb1..14f02cd2b8a19e8581a170dfba2b948ef8304203 100644
--- a/htl/pt-create.c
+++ b/htl/pt-create.c
@@ -228,7 +228,7 @@ __pthread_create_internal (struct __pthread **thread,
the number of threads from within the new thread isn't an option
since this thread might return and call `pthread_exit' before the
new thread runs. */
- atomic_increment (&__pthread_total);
+ atomic_fetch_add_relaxed (&__pthread_total, 1);
/* Store a pointer to this thread in the thread ID lookup table. We
could use __thread_setid, however, we only lock for reading as no
diff --git a/manual/ipc.texi b/manual/ipc.texi
index 081b98fe29e0b3b5b7f4f916ad2085d170bd3825..f7cbdc3e09b0b4aea9a96ddcaf571c474024cc32 100644
--- a/manual/ipc.texi
+++ b/manual/ipc.texi
@@ -85,7 +85,7 @@ by @theglibc{}.
@deftypefun int sem_wait (sem_t *@var{sem});
@safety{@prelim{}@mtsafe{}@assafe{}@acunsafe{@acucorrupt{}}}
-@c atomic_increment (nwaiters) acucorrupt
+@c atomic_fetch_add_relaxed (nwaiters) acucorrupt
@c
@c Given the use atomic operations this function seems
@c to be AS-safe. It is AC-unsafe because there is still
diff --git a/manual/llio.texi b/manual/llio.texi
index 92bfd93e067ce2a782369084ed7dae099300f418..4e6e3fb672bb8ecbb1bb52faf3d70d9b7b33973f 100644
--- a/manual/llio.texi
+++ b/manual/llio.texi
@@ -2528,7 +2528,7 @@ aiocb64}, since the LFS transparently replaces the old interface.
@c _dl_allocate_tls_init ok
@c GET_DTV ok
@c mmap ok
-@c atomic_increment_val ok
+@c atomic_fetch_add_relaxed ok
@c munmap ok
@c change_stack_perm ok
@c mprotect ok
@@ -2567,7 +2567,7 @@ aiocb64}, since the LFS transparently replaces the old interface.
@c do_clone @asulock @ascuheap @aculock @acsmem
@c PREPARE_CREATE ok
@c lll_lock (pd->lock) @asulock @aculock
-@c atomic_increment ok
+@c atomic_fetch_add_relaxed ok
@c clone ok
@c atomic_decrement ok
@c atomic_exchange_acquire ok
diff --git a/nptl/nptl_setxid.c b/nptl/nptl_setxid.c
index aa863c7ea8122ea01d1aa4cffe101bbb7c11270c..3b7e2d434abe8a15145349d1a08a4e706061c74d 100644
--- a/nptl/nptl_setxid.c
+++ b/nptl/nptl_setxid.c
@@ -163,7 +163,7 @@ setxid_signal_thread (struct xid_command *cmdp, struct pthread *t)
/* If this failed, it must have had not started yet or else exited. */
if (!INTERNAL_SYSCALL_ERROR_P (val))
{
- atomic_increment (&cmdp->cntr);
+ atomic_fetch_add_relaxed (&cmdp->cntr, 1);
return 1;
}
else
diff --git a/nptl/pthread_create.c b/nptl/pthread_create.c
index 8533d609684bc6681fbdccd9f2635d03ef3aa937..2602dba54e872f36bd54955af7587378e5dc3812 100644
--- a/nptl/pthread_create.c
+++ b/nptl/pthread_create.c
@@ -759,7 +759,7 @@ __pthread_create_2_1 (pthread_t *newthread, const pthread_attr_t *attr,
we momentarily store a false value; this doesn't matter because there
is no kosher thing a signal handler interrupting us right here can do
that cares whether the thread count is correct. */
- atomic_increment (&__nptl_nthreads);
+ atomic_fetch_add_relaxed (&__nptl_nthreads, 1);
/* Our local value of stopped_start and thread_ran can be accessed at
any time. The PD->stopped_start may only be accessed if we have
diff --git a/nptl/sem_post.c b/nptl/sem_post.c
index 9e5741753a741034db96cfff8b8978908fafc1f6..7ec21e92eb4c71d7f17764e96bc7603837f7522d 100644
--- a/nptl/sem_post.c
+++ b/nptl/sem_post.c
@@ -91,7 +91,7 @@ __old_sem_post (sem_t *sem)
/* We must need to synchronize with consumers of this token, so the atomic
increment must have release MO semantics. */
atomic_write_barrier ();
- (void) atomic_increment_val (futex);
+ atomic_fetch_add_release (futex, 1);
/* We always have to assume it is a shared semaphore. */
futex_wake (futex, 1, LLL_SHARED);
return 0;
diff --git a/nscd/cache.c b/nscd/cache.c
index b66c35334a79a315ac9fd533df09ec097221d8e0..21af9a0f9550dfc7c1121fb5014cd80acdfcf696 100644
--- a/nscd/cache.c
+++ b/nscd/cache.c
@@ -192,7 +192,7 @@ cache_add (int type, const void *key, size_t len, struct datahead *packet,
/* We depend on this value being correct and at least as high as the
real number of entries. */
- atomic_increment (&table->head->nentries);
+ atomic_fetch_add_relaxed (&table->head->nentries, 1);
/* It does not matter that we are not loading the just increment
value, this is just for statistics. */
diff --git a/nscd/nscd_helper.c b/nscd/nscd_helper.c
index 8e66fa2548e87c9b24cade41339c83f4cef7f2cf..d3e05e272a854e13c0e4d18594ea57336b8db2bf 100644
--- a/nscd/nscd_helper.c
+++ b/nscd/nscd_helper.c
@@ -425,7 +425,7 @@ __nscd_get_map_ref (request_type type, const char *name,
0))
cur = NO_MAPPING;
else
- atomic_increment (&cur->counter);
+ atomic_fetch_add_relaxed (&cur->counter, 1);
}
}
diff --git a/sysdeps/unix/sysv/linux/check_pf.c b/sysdeps/unix/sysv/linux/check_pf.c
index 4d486ca9b5026c7a7950bd7c7155212966df3c44..0b77a2d897027edc36e956301f018c2ab0121444 100644
--- a/sysdeps/unix/sysv/linux/check_pf.c
+++ b/sysdeps/unix/sysv/linux/check_pf.c
@@ -72,8 +72,8 @@ static uint32_t nl_timestamp;
uint32_t
__bump_nl_timestamp (void)
{
- if (atomic_increment_val (&nl_timestamp) == 0)
- atomic_increment (&nl_timestamp);
+ if (atomic_fetch_add_relaxed (&nl_timestamp, 1) + 1 == 0)
+ atomic_fetch_add_relaxed (&nl_timestamp, 1);
return nl_timestamp;
}
@@ -309,7 +309,7 @@ __check_pf (bool *seen_ipv4, bool *seen_ipv6,
if (cache_valid_p ())
{
data = cache;
- atomic_increment (&cache->usecnt);
+ atomic_fetch_add_relaxed (&cache->usecnt, 1);
}
else
{
next reply other threads:[~2022-09-08 14:02 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-08 14:01 Wilco Dijkstra [this message]
2022-09-21 17:17 ` Adhemerval Zanella Netto
2022-09-22 13:27 ` Wilco Dijkstra
2022-09-23 13:26 ` Adhemerval Zanella Netto
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