public inbox for glibc-cvs@sourceware.org
help / color / mirror / Atom feed
* [glibc/users/skpgkp2/2.33/master] nptl: Effectively skip CAS in spinlock loop
@ 2022-09-28 19:11 Sunil Pandey
0 siblings, 0 replies; 3+ messages in thread
From: Sunil Pandey @ 2022-09-28 19:11 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=2574fdfc0f7ed7fe2586bd906e6076912af6cd86
commit 2574fdfc0f7ed7fe2586bd906e6076912af6cd86
Author: Jangwoong Kim <6812skiii@gmail.com>
Date: Tue Dec 14 21:30:51 2021 +0900
nptl: Effectively skip CAS in spinlock loop
The commit:
"Add LLL_MUTEX_READ_LOCK [BZ #28537]"
SHA1: d672a98a1af106bd68deb15576710cd61363f7a6
introduced LLL_MUTEX_READ_LOCK, to skip CAS in spinlock loop
if atomic load fails. But, "continue" inside of do-while loop
does not skip the evaluation of escape expression, thus CAS
is not skipped.
Replace do-while with while and skip LLL_MUTEX_TRYLOCK if
LLL_MUTEX_READ_LOCK fails.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
(cherry picked from commit 6b8dbbd03ac88f169b65b5c7d7278576a11d2e44)
Diff:
---
nptl/pthread_mutex_lock.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/nptl/pthread_mutex_lock.c b/nptl/pthread_mutex_lock.c
index 2895926953..253743f76c 100644
--- a/nptl/pthread_mutex_lock.c
+++ b/nptl/pthread_mutex_lock.c
@@ -138,10 +138,9 @@ __pthread_mutex_lock (pthread_mutex_t *mutex)
break;
}
atomic_spin_nop ();
- if (LLL_MUTEX_READ_LOCK (mutex) != 0)
- continue;
}
- while (LLL_MUTEX_TRYLOCK (mutex) != 0);
+ while (LLL_MUTEX_READ_LOCK (mutex) != 0
+ || LLL_MUTEX_TRYLOCK (mutex) != 0);
mutex->__data.__spins += (cnt - mutex->__data.__spins) / 8;
}
^ permalink raw reply [flat|nested] 3+ messages in thread
* [glibc/users/skpgkp2/2.33/master] nptl: Effectively skip CAS in spinlock loop
@ 2022-09-28 21:45 Sunil Pandey
0 siblings, 0 replies; 3+ messages in thread
From: Sunil Pandey @ 2022-09-28 21:45 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=49479d237f678b53700689085e075d1382e401de
commit 49479d237f678b53700689085e075d1382e401de
Author: Jangwoong Kim <6812skiii@gmail.com>
Date: Tue Dec 14 21:30:51 2021 +0900
nptl: Effectively skip CAS in spinlock loop
The commit:
"Add LLL_MUTEX_READ_LOCK [BZ #28537]"
SHA1: d672a98a1af106bd68deb15576710cd61363f7a6
introduced LLL_MUTEX_READ_LOCK, to skip CAS in spinlock loop
if atomic load fails. But, "continue" inside of do-while loop
does not skip the evaluation of escape expression, thus CAS
is not skipped.
Replace do-while with while and skip LLL_MUTEX_TRYLOCK if
LLL_MUTEX_READ_LOCK fails.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
(cherry picked from commit 6b8dbbd03ac88f169b65b5c7d7278576a11d2e44)
Diff:
---
nptl/pthread_mutex_lock.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/nptl/pthread_mutex_lock.c b/nptl/pthread_mutex_lock.c
index 2895926953..253743f76c 100644
--- a/nptl/pthread_mutex_lock.c
+++ b/nptl/pthread_mutex_lock.c
@@ -138,10 +138,9 @@ __pthread_mutex_lock (pthread_mutex_t *mutex)
break;
}
atomic_spin_nop ();
- if (LLL_MUTEX_READ_LOCK (mutex) != 0)
- continue;
}
- while (LLL_MUTEX_TRYLOCK (mutex) != 0);
+ while (LLL_MUTEX_READ_LOCK (mutex) != 0
+ || LLL_MUTEX_TRYLOCK (mutex) != 0);
mutex->__data.__spins += (cnt - mutex->__data.__spins) / 8;
}
^ permalink raw reply [flat|nested] 3+ messages in thread
* [glibc/users/skpgkp2/2.33/master] nptl: Effectively skip CAS in spinlock loop
@ 2022-09-29 18:41 Sunil Pandey
0 siblings, 0 replies; 3+ messages in thread
From: Sunil Pandey @ 2022-09-29 18:41 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=8b9ad5ec93ce8941a1e53cc3beea84293d998d2c
commit 8b9ad5ec93ce8941a1e53cc3beea84293d998d2c
Author: Jangwoong Kim <6812skiii@gmail.com>
Date: Tue Dec 14 21:30:51 2021 +0900
nptl: Effectively skip CAS in spinlock loop
The commit:
"Add LLL_MUTEX_READ_LOCK [BZ #28537]"
SHA1: d672a98a1af106bd68deb15576710cd61363f7a6
introduced LLL_MUTEX_READ_LOCK, to skip CAS in spinlock loop
if atomic load fails. But, "continue" inside of do-while loop
does not skip the evaluation of escape expression, thus CAS
is not skipped.
Replace do-while with while and skip LLL_MUTEX_TRYLOCK if
LLL_MUTEX_READ_LOCK fails.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
(cherry picked from commit 6b8dbbd03ac88f169b65b5c7d7278576a11d2e44)
Diff:
---
nptl/pthread_mutex_lock.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/nptl/pthread_mutex_lock.c b/nptl/pthread_mutex_lock.c
index 2895926953..253743f76c 100644
--- a/nptl/pthread_mutex_lock.c
+++ b/nptl/pthread_mutex_lock.c
@@ -138,10 +138,9 @@ __pthread_mutex_lock (pthread_mutex_t *mutex)
break;
}
atomic_spin_nop ();
- if (LLL_MUTEX_READ_LOCK (mutex) != 0)
- continue;
}
- while (LLL_MUTEX_TRYLOCK (mutex) != 0);
+ while (LLL_MUTEX_READ_LOCK (mutex) != 0
+ || LLL_MUTEX_TRYLOCK (mutex) != 0);
mutex->__data.__spins += (cnt - mutex->__data.__spins) / 8;
}
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2022-09-29 18:41 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-09-28 19:11 [glibc/users/skpgkp2/2.33/master] nptl: Effectively skip CAS in spinlock loop Sunil Pandey
2022-09-28 21:45 Sunil Pandey
2022-09-29 18:41 Sunil Pandey
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).