* [PATCH] Use C11 atomics instead of atomic_decrement(_val)
@ 2022-09-08 14:09 Wilco Dijkstra
2022-09-08 20:12 ` DJ Delorie
0 siblings, 1 reply; 3+ messages in thread
From: Wilco Dijkstra @ 2022-09-08 14:09 UTC (permalink / raw)
To: 'GNU C Library'; +Cc: Adhemerval Zanella
Replace atomic_decrement and atomic_decrement_val with atomic_fetch_add_relaxed.
Passes regress on AArch64.
---
diff --git a/htl/pt-create.c b/htl/pt-create.c
index 14f02cd2b8a19e8581a170dfba2b948ef8304203..5d37edbbffb16b7cbb6db133016653227fc45f47 100644
--- a/htl/pt-create.c
+++ b/htl/pt-create.c
@@ -262,7 +262,7 @@ failed_starting:
}
__pthread_setid (pthread->thread, NULL);
- atomic_decrement (&__pthread_total);
+ atomic_fetch_add_relaxed (&__pthread_total, -1);
failed_sigstate:
__pthread_sigstate_destroy (pthread);
failed_setup:
diff --git a/malloc/malloc.c b/malloc/malloc.c
index adafef9d5a7b3c323bd6307c8d15f7f1921f0192..4bd95d81ae51c8ad33d8e30c83f681688c41723d 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -3033,7 +3033,7 @@ munmap_chunk (mchunkptr p)
|| __glibc_unlikely (!powerof2 (mem & (pagesize - 1))))
malloc_printerr ("munmap_chunk(): invalid pointer");
- atomic_decrement (&mp_.n_mmaps);
+ atomic_fetch_add_relaxed (&mp_.n_mmaps, -1);
atomic_fetch_add_relaxed (&mp_.mmapped_mem, -total_size);
/* If munmap failed the process virtual memory address space is in a
diff --git a/manual/ipc.texi b/manual/ipc.texi
index f7cbdc3e09b0b4aea9a96ddcaf571c474024cc32..be74664af9c146dd3024b080e90b7ca9834b14ef 100644
--- a/manual/ipc.texi
+++ b/manual/ipc.texi
@@ -89,7 +89,7 @@ by @theglibc{}.
@c
@c Given the use atomic operations this function seems
@c to be AS-safe. It is AC-unsafe because there is still
-@c a window between atomic_decrement and the pthread_push
+@c a window between atomic_fetch_add_relaxed and the pthread_push
@c of the handler that undoes that operation. A cancellation
@c at that point would fail to remove the process from the
@c waiters count.
diff --git a/manual/llio.texi b/manual/llio.texi
index eba9a0e6593f17116b41ff302cfca05846727155..1b801ee817db2935d8866894be23ffa516690ca3 100644
--- a/manual/llio.texi
+++ b/manual/llio.texi
@@ -2569,7 +2569,7 @@ aiocb64}, since the LFS transparently replaces the old interface.
@c lll_lock (pd->lock) @asulock @aculock
@c atomic_fetch_add_relaxed ok
@c clone ok
-@c atomic_decrement ok
+@c atomic_fetch_add_relaxed ok
@c atomic_exchange_acquire ok
@c lll_futex_wake ok
@c deallocate_stack dup
diff --git a/nptl/nptl_setxid.c b/nptl/nptl_setxid.c
index 3b7e2d434abe8a15145349d1a08a4e706061c74d..301809d200d1ac6c89fbf100e553c5713f326ed7 100644
--- a/nptl/nptl_setxid.c
+++ b/nptl/nptl_setxid.c
@@ -88,7 +88,7 @@ __nptl_setxid_sighandler (int sig, siginfo_t *si, void *ctx)
self->setxid_futex = 1;
futex_wake (&self->setxid_futex, 1, FUTEX_PRIVATE);
- if (atomic_decrement_val (&xidcmd->cntr) == 0)
+ if (atomic_fetch_add_relaxed (&xidcmd->cntr, -1) == 1)
futex_wake ((unsigned int *) &xidcmd->cntr, 1, FUTEX_PRIVATE);
}
libc_hidden_def (__nptl_setxid_sighandler)
diff --git a/nptl/pthread_create.c b/nptl/pthread_create.c
index ada3fdd4d440c3fdcf4567734a452c8ba4d0fce1..32ae2f4b2fcb81d057c6cea68182af20f8a4e1f9 100644
--- a/nptl/pthread_create.c
+++ b/nptl/pthread_create.c
@@ -861,7 +861,7 @@ __pthread_create_2_1 (pthread_t *newthread, const pthread_attr_t *attr,
NOTES above). */
/* Oops, we lied for a second. */
- atomic_decrement (&__nptl_nthreads);
+ atomic_fetch_add_relaxed (&__nptl_nthreads, -1);
/* Free the resources. */
__nptl_deallocate_stack (pd);
diff --git a/nscd/nscd-client.h b/nscd/nscd-client.h
index fee2a15dcc323258cecd45c5fb8e472da9161792..ca9e6def1a88ff14c5e8b39f0e236aa8a30f95ae 100644
--- a/nscd/nscd-client.h
+++ b/nscd/nscd-client.h
@@ -421,7 +421,7 @@ __nscd_drop_map_ref (struct mapped_database *map, int *gc_cycle)
return -1;
}
- if (atomic_decrement_val (&map->counter) == 0)
+ if (atomic_fetch_add_relaxed (&map->counter, -1) == 1)
__nscd_unmap (map);
}
diff --git a/nscd/nscd_getai.c b/nscd/nscd_getai.c
index a99a4d8142b89521f3ca1759f42d5d88e1103f61..8e4650ebaedc6d79bd5ccda6721551b0227dbbb5 100644
--- a/nscd/nscd_getai.c
+++ b/nscd/nscd_getai.c
@@ -198,7 +198,7 @@ __nscd_getai (const char *key, struct nscd_ai_result **result, int *h_errnop)
if ((gc_cycle & 1) != 0 || ++nretries == 5 || retval == -1)
{
/* nscd is just running gc now. Disable using the mapping. */
- if (atomic_decrement_val (&mapped->counter) == 0)
+ if (atomic_fetch_add_relaxed (&mapped->counter, -1) == 1)
__nscd_unmap (mapped);
mapped = NO_MAPPING;
}
diff --git a/nscd/nscd_getgr_r.c b/nscd/nscd_getgr_r.c
index 3636c031ec9403c7b447ebc52eecb2c60d74740f..bde3b588a01274730e1b1d817dfff62fd4f60c15 100644
--- a/nscd/nscd_getgr_r.c
+++ b/nscd/nscd_getgr_r.c
@@ -312,7 +312,7 @@ nscd_getgr_r (const char *key, size_t keylen, request_type type,
if ((gc_cycle & 1) != 0 || ++nretries == 5 || retval == -1)
{
/* nscd is just running gc now. Disable using the mapping. */
- if (atomic_decrement_val (&mapped->counter) == 0)
+ if (atomic_fetch_add_relaxed (&mapped->counter, -1) == 1)
__nscd_unmap (mapped);
mapped = NO_MAPPING;
}
diff --git a/nscd/nscd_gethst_r.c b/nscd/nscd_gethst_r.c
index 9becb620335d14d7becebe6c29ad96cc4e7463ee..31d13580a11e64792d6f02ecd7437884d4436eb3 100644
--- a/nscd/nscd_gethst_r.c
+++ b/nscd/nscd_gethst_r.c
@@ -440,7 +440,7 @@ nscd_gethst_r (const char *key, size_t keylen, request_type type,
if ((gc_cycle & 1) != 0 || ++nretries == 5 || retval == -1)
{
/* nscd is just running gc now. Disable using the mapping. */
- if (atomic_decrement_val (&mapped->counter) == 0)
+ if (atomic_fetch_add_relaxed (&mapped->counter, -1) == 1)
__nscd_unmap (mapped);
mapped = NO_MAPPING;
}
diff --git a/nscd/nscd_getpw_r.c b/nscd/nscd_getpw_r.c
index 20986f44332fca42d2f43794b4c365f6b3968cae..82fdd17d8c39287a9d450ff25802116028dc9475 100644
--- a/nscd/nscd_getpw_r.c
+++ b/nscd/nscd_getpw_r.c
@@ -225,7 +225,7 @@ nscd_getpw_r (const char *key, size_t keylen, request_type type,
if ((gc_cycle & 1) != 0 || ++nretries == 5 || retval == -1)
{
/* nscd is just running gc now. Disable using the mapping. */
- if (atomic_decrement_val (&mapped->counter) == 0)
+ if (atomic_fetch_add_relaxed (&mapped->counter, -1) == 1)
__nscd_unmap (mapped);
mapped = NO_MAPPING;
}
diff --git a/nscd/nscd_getserv_r.c b/nscd/nscd_getserv_r.c
index 42b875d024c674a6c46dd28be8308a8d5d650ca6..de843b33631e2c57ac4e0192c6f1027c586cf329 100644
--- a/nscd/nscd_getserv_r.c
+++ b/nscd/nscd_getserv_r.c
@@ -365,7 +365,7 @@ nscd_getserv_r (const char *crit, size_t critlen, const char *proto,
if ((gc_cycle & 1) != 0 || ++nretries == 5 || retval == -1)
{
/* nscd is just running gc now. Disable using the mapping. */
- if (atomic_decrement_val (&mapped->counter) == 0)
+ if (atomic_fetch_add_relaxed (&mapped->counter, -1) == 1)
__nscd_unmap (mapped);
mapped = NO_MAPPING;
}
diff --git a/nscd/nscd_helper.c b/nscd/nscd_helper.c
index d3e05e272a854e13c0e4d18594ea57336b8db2bf..fc41bfdb6eebb880d6132ea5cf409ca657570f82 100644
--- a/nscd/nscd_helper.c
+++ b/nscd/nscd_helper.c
@@ -390,7 +390,7 @@ __nscd_get_mapping (request_type type, const char *key,
struct mapped_database *oldval = *mappedp;
*mappedp = result;
- if (oldval != NULL && atomic_decrement_val (&oldval->counter) == 0)
+ if (oldval != NULL && atomic_fetch_add_relaxed (&oldval->counter, -1) == 1)
__nscd_unmap (oldval);
return result;
diff --git a/nscd/nscd_initgroups.c b/nscd/nscd_initgroups.c
index dfce76a06090d5bd2869f8a239bdef51866bd854..47b6deb0699eaa984691388d146ae5e01ddd83ab 100644
--- a/nscd/nscd_initgroups.c
+++ b/nscd/nscd_initgroups.c
@@ -166,7 +166,7 @@ __nscd_getgrouplist (const char *user, gid_t group, long int *size,
if ((gc_cycle & 1) != 0 || ++nretries == 5 || retval == -1)
{
/* nscd is just running gc now. Disable using the mapping. */
- if (atomic_decrement_val (&mapped->counter) == 0)
+ if (atomic_fetch_add_relaxed (&mapped->counter, -1) == 1)
__nscd_unmap (mapped);
mapped = NO_MAPPING;
}
diff --git a/nscd/nscd_netgroup.c b/nscd/nscd_netgroup.c
index 7e51dd3d941e383ab97bc0f70dd4dda65c340e0b..11b7f3214c2fb08f2e08df86f0d984e7bfc9bda2 100644
--- a/nscd/nscd_netgroup.c
+++ b/nscd/nscd_netgroup.c
@@ -148,7 +148,7 @@ __nscd_setnetgrent (const char *group, struct __netgrent *datap)
if ((gc_cycle & 1) != 0 || ++nretries == 5 || retval == -1)
{
/* nscd is just running gc now. Disable using the mapping. */
- if (atomic_decrement_val (&mapped->counter) == 0)
+ if (atomic_fetch_add_relaxed (&mapped->counter, -1) == 1)
__nscd_unmap (mapped);
mapped = NO_MAPPING;
}
@@ -272,7 +272,7 @@ __nscd_innetgr (const char *netgroup, const char *host, const char *user,
if ((gc_cycle & 1) != 0 || ++nretries == 5 || retval == -1)
{
/* nscd is just running gc now. Disable using the mapping. */
- if (atomic_decrement_val (&mapped->counter) == 0)
+ if (atomic_fetch_add_relaxed (&mapped->counter, -1) == 1)
__nscd_unmap (mapped);
mapped = NO_MAPPING;
}
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] Use C11 atomics instead of atomic_decrement(_val)
2022-09-08 14:09 [PATCH] Use C11 atomics instead of atomic_decrement(_val) Wilco Dijkstra
@ 2022-09-08 20:12 ` DJ Delorie
2022-09-09 14:02 ` Wilco Dijkstra
0 siblings, 1 reply; 3+ messages in thread
From: DJ Delorie @ 2022-09-08 20:12 UTC (permalink / raw)
To: Wilco Dijkstra; +Cc: libc-alpha
atomic_decrement returns the NEW value
atomic_fetch_add_relaxed returns the OLD value
Wilco Dijkstra via Libc-alpha <libc-alpha@sourceware.org> writes:
> - atomic_decrement (&__pthread_total);
> + atomic_fetch_add_relaxed (&__pthread_total, -1);
Ok.
> - atomic_decrement (&mp_.n_mmaps);
> + atomic_fetch_add_relaxed (&mp_.n_mmaps, -1);
Ok.
> +++ b/manual/ipc.texi
> @@ -89,7 +89,7 @@ by @theglibc{}.
> @c
> @c Given the use atomic operations this function seems
> @c to be AS-safe. It is AC-unsafe because there is still
> -@c a window between atomic_decrement and the pthread_push
> +@c a window between atomic_fetch_add_relaxed and the pthread_push
Ok.
> +++ b/manual/llio.texi
> @@ -2569,7 +2569,7 @@ aiocb64}, since the LFS transparently replaces the old interface.
> @c lll_lock (pd->lock) @asulock @aculock
> @c atomic_fetch_add_relaxed ok
> @c clone ok
> -@c atomic_decrement ok
> +@c atomic_fetch_add_relaxed ok
Ok.
> - if (atomic_decrement_val (&xidcmd->cntr) == 0)
> + if (atomic_fetch_add_relaxed (&xidcmd->cntr, -1) == 1)
Ok. See note at beginning for why ;-)
> /* Oops, we lied for a second. */
> - atomic_decrement (&__nptl_nthreads);
> + atomic_fetch_add_relaxed (&__nptl_nthreads, -1);
Ok.
> - if (atomic_decrement_val (&map->counter) == 0)
> + if (atomic_fetch_add_relaxed (&map->counter, -1) == 1)
Ok.
> - if (atomic_decrement_val (&mapped->counter) == 0)
> + if (atomic_fetch_add_relaxed (&mapped->counter, -1) == 1)
Ok.
> - if (atomic_decrement_val (&mapped->counter) == 0)
> + if (atomic_fetch_add_relaxed (&mapped->counter, -1) == 1)
Ok.
> - if (atomic_decrement_val (&mapped->counter) == 0)
> + if (atomic_fetch_add_relaxed (&mapped->counter, -1) == 1)
Ok.
> - if (atomic_decrement_val (&mapped->counter) == 0)
> + if (atomic_fetch_add_relaxed (&mapped->counter, -1) == 1)
Ok.
> - if (atomic_decrement_val (&mapped->counter) == 0)
> + if (atomic_fetch_add_relaxed (&mapped->counter, -1) == 1)
Ok.
> - if (oldval != NULL && atomic_decrement_val (&oldval->counter) == 0)
> + if (oldval != NULL && atomic_fetch_add_relaxed (&oldval->counter, -1) == 1)
Ok.
> - if (atomic_decrement_val (&mapped->counter) == 0)
> + if (atomic_fetch_add_relaxed (&mapped->counter, -1) == 1)
Ok.
> - if (atomic_decrement_val (&mapped->counter) == 0)
> + if (atomic_fetch_add_relaxed (&mapped->counter, -1) == 1)
Ok.
> - if (atomic_decrement_val (&mapped->counter) == 0)
> + if (atomic_fetch_add_relaxed (&mapped->counter, -1) == 1)
Ok.
LGTM.
Reviewed-by: DJ Delorie <dj@redhat.com>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] Use C11 atomics instead of atomic_decrement(_val)
2022-09-08 20:12 ` DJ Delorie
@ 2022-09-09 14:02 ` Wilco Dijkstra
0 siblings, 0 replies; 3+ messages in thread
From: Wilco Dijkstra @ 2022-09-09 14:02 UTC (permalink / raw)
To: DJ Delorie; +Cc: libc-alpha
Hi DJ,
Thanks for the review.
> atomic_decrement returns the NEW value
> atomic_fetch_add_relaxed returns the OLD value
Indeed, this series of patches replaces the many different variations of atomic
add with a single one that directly maps to the GCC builtin (and the underlying
atomic operation).
GCC also has __atomic_add_fetch which returns the new value, so once all this
code has been cleaned up we could add support for that.
Cheers,
Wilco
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2022-09-09 14:02 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-09-08 14:09 [PATCH] Use C11 atomics instead of atomic_decrement(_val) Wilco Dijkstra
2022-09-08 20:12 ` DJ Delorie
2022-09-09 14:02 ` Wilco Dijkstra
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).