From: Sunil Dora Date: Tue, 17 Jun 2025 10:08:52 +0000 (-0700) Subject: glibc: nptl Use a single loop in pthread_cond_wait instaed of a nested loop X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=eab44f7a027414ef29f6d07617997cc50fc515cd;p=thirdparty%2Fopenembedded%2Fopenembedded-core-contrib.git glibc: nptl Use a single loop in pthread_cond_wait instaed of a nested loop The following commits have been cherry-picked from Glibc master branch: Bug : https://sourceware.org/bugzilla/show_bug.cgi?id=25847 Upstream-Status: Backport [https://sourceware.org/git/?p=glibc.git;a=commit;h=929a4764ac90382616b6a21f099192b2475da674] Signed-off-by: Sunil Dora Signed-off-by: Steve Sakoman --- diff --git a/meta/recipes-core/glibc/glibc/0026-PR25847-5.patch b/meta/recipes-core/glibc/glibc/0026-PR25847-5.patch new file mode 100644 index 0000000000..16fe6f8460 --- /dev/null +++ b/meta/recipes-core/glibc/glibc/0026-PR25847-5.patch @@ -0,0 +1,105 @@ +From d9ffb50dc55f77e584a5d0275eea758c7a6b04e3 Mon Sep 17 00:00:00 2001 +From: Malte Skarupke +Date: Mon, 16 Jun 2025 23:53:35 -0700 +Subject: [PATCH] nptl: Use a single loop in pthread_cond_wait instaed of a + nested loop + +The loop was a little more complicated than necessary. There was only one +break statement out of the inner loop, and the outer loop was nearly empty. +So just remove the outer loop, moving its code to the one break statement in +the inner loop. This allows us to replace all gotos with break statements. + +The following commits have been cherry-picked from Glibc master branch: +Bug : https://sourceware.org/bugzilla/show_bug.cgi?id=25847 + +Upstream-Status: Backport +[https://sourceware.org/git/?p=glibc.git;a=commit;h=929a4764ac90382616b6a21f099192b2475da674] + +Signed-off-by: Sunil Dora +--- + nptl/pthread_cond_wait.c | 41 +++++++++++++++++++--------------------- + 1 file changed, 19 insertions(+), 22 deletions(-) + +diff --git a/nptl/pthread_cond_wait.c b/nptl/pthread_cond_wait.c +index 47e834cade..5c86880105 100644 +--- a/nptl/pthread_cond_wait.c ++++ b/nptl/pthread_cond_wait.c +@@ -410,17 +410,15 @@ __pthread_cond_wait_common (pthread_cond_t *cond, pthread_mutex_t *mutex, + return err; + } + +- /* Now wait until a signal is available in our group or it is closed. +- Acquire MO so that if we observe (signals == lowseq) after group +- switching in __condvar_quiesce_and_switch_g1, we synchronize with that +- store and will see the prior update of __g1_start done while switching +- groups too. */ +- unsigned int signals = atomic_load_acquire (cond->__data.__g_signals + g); +- +- do +- { ++ + while (1) + { ++ /* Now wait until a signal is available in our group or it is closed. ++ Acquire MO so that if we observe (signals == lowseq) after group ++ switching in __condvar_quiesce_and_switch_g1, we synchronize with that ++ store and will see the prior update of __g1_start done while switching ++ groups too. */ ++ unsigned int signals = atomic_load_acquire (cond->__data.__g_signals + g); + uint64_t g1_start = __condvar_load_g1_start_relaxed (cond); + unsigned int lowseq = (g1_start & 1) == g ? signals : g1_start & ~1U; + +@@ -429,7 +427,7 @@ __pthread_cond_wait_common (pthread_cond_t *cond, pthread_mutex_t *mutex, + /* If the group is closed already, + then this waiter originally had enough extra signals to + consume, up until the time its group was closed. */ +- goto done; ++ break; + } + + /* If there is an available signal, don't block. +@@ -438,8 +436,16 @@ __pthread_cond_wait_common (pthread_cond_t *cond, pthread_mutex_t *mutex, + G2, but in either case we're allowed to consume the available + signal and should not block anymore. */ + if ((int)(signals - lowseq) >= 2) +- break; +- ++ { ++ /* Try to grab a signal. See above for MO. (if we do another loop ++ iteration we need to see the correct value of g1_start) */ ++ if (atomic_compare_exchange_weak_acquire ( ++ cond->__data.__g_signals + g, ++ &signals, signals - 2)) ++ break; ++ else ++ continue; ++ } + /* No signals available after spinning, so prepare to block. + We first acquire a group reference and use acquire MO for that so + that we synchronize with the dummy read-modify-write in +@@ -479,21 +485,12 @@ __pthread_cond_wait_common (pthread_cond_t *cond, pthread_mutex_t *mutex, + the lock during cancellation is not possible. */ + __condvar_cancel_waiting (cond, seq, g, private); + result = err; +- goto done; ++ break; + } + else + __condvar_dec_grefs (cond, g, private); + +- /* Reload signals. See above for MO. */ +- signals = atomic_load_acquire (cond->__data.__g_signals + g); + } +- } +- /* Try to grab a signal. See above for MO. (if we do another loop +- iteration we need to see the correct value of g1_start) */ +- while (!atomic_compare_exchange_weak_acquire (cond->__data.__g_signals + g, +- &signals, signals - 2)); +- +- done: + + /* Confirm that we have been woken. We do that before acquiring the mutex + to allow for execution of pthread_cond_destroy while having acquired the +-- +2.49.0 + diff --git a/meta/recipes-core/glibc/glibc_2.35.bb b/meta/recipes-core/glibc/glibc_2.35.bb index bb5d22cfe8..04dcb22c3d 100644 --- a/meta/recipes-core/glibc/glibc_2.35.bb +++ b/meta/recipes-core/glibc/glibc_2.35.bb @@ -66,6 +66,7 @@ SRC_URI = "${GLIBC_GIT_URI};branch=${SRCBRANCH};name=glibc \ file://0026-PR25847-2.patch \ file://0026-PR25847-3.patch \ file://0026-PR25847-4.patch \ + file://0026-PR25847-5.patch \ \ file://0001-Revert-Linux-Implement-a-useful-version-of-_startup_.patch \ file://0002-get_nscd_addresses-Fix-subscript-typos-BZ-29605.patch \