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| author | Roland McGrath <roland@hack.frob.com> | 2014-06-26 09:31:11 -0700 |
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| committer | Roland McGrath <roland@hack.frob.com> | 2014-06-26 09:31:11 -0700 |
| commit | 52ae23b4bfa09fa1f42e3f659aaa057d1176d06b (patch) | |
| tree | 7c61e56d7fbbb3c9f82994b5d3d778cc19ee48c2 /sysdeps/unix/sysv/linux/s390/elision-trylock.c | |
| parent | 39507e4a6c52d67780d194dae8cfb636e2dbb87e (diff) | |
| download | glibc-52ae23b4bfa09fa1f42e3f659aaa057d1176d06b.zip glibc-52ae23b4bfa09fa1f42e3f659aaa057d1176d06b.tar.gz glibc-52ae23b4bfa09fa1f42e3f659aaa057d1176d06b.tar.bz2 | |
Move remaining S390 code out of nptl/.
Diffstat (limited to 'sysdeps/unix/sysv/linux/s390/elision-trylock.c')
| -rw-r--r-- | sysdeps/unix/sysv/linux/s390/elision-trylock.c | 94 |
1 files changed, 94 insertions, 0 deletions
diff --git a/sysdeps/unix/sysv/linux/s390/elision-trylock.c b/sysdeps/unix/sysv/linux/s390/elision-trylock.c new file mode 100644 index 0000000..61447d6 --- /dev/null +++ b/sysdeps/unix/sysv/linux/s390/elision-trylock.c @@ -0,0 +1,94 @@ +/* Elided pthread mutex trylock. + Copyright (C) 2014 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + <http://www.gnu.org/licenses/>. */ + +#include <pthread.h> +#include <pthreadP.h> +#include <lowlevellock.h> +#include <htmintrin.h> +#include <elision-conf.h> + +#define aconf __elision_aconf + +/* Try to elide a futex trylock. FUTEX is the futex variable. ADAPT_COUNT is + the adaptation counter in the mutex. */ + +int +__lll_trylock_elision (int *futex, short *adapt_count) +{ + __asm__ volatile (".machinemode \"zarch_nohighgprs\"\n\t" + ".machine \"all\"" + : : : "memory"); + + /* Implement POSIX semantics by forbiding nesting elided trylocks. + Sorry. After the abort the code is re-executed + non transactional and if the lock was already locked + return an error. */ + if (__builtin_tx_nesting_depth () > 0) + { + /* Note that this abort may terminate an outermost transaction that + was created outside glibc. + This persistently aborts the current transactions to force + them to use the default lock instead of retrying transactions + until their try_tbegin is zero. + */ + __builtin_tabort (_HTM_FIRST_USER_ABORT_CODE | 1); + } + + /* Only try a transaction if it's worth it. */ + if (*adapt_count <= 0) + { + unsigned status; + + if (__builtin_expect + ((status = __builtin_tbegin ((void *)0)) == _HTM_TBEGIN_STARTED, 1)) + { + if (*futex == 0) + return 0; + /* Lock was busy. Fall back to normal locking. */ + /* Since we are in a non-nested transaction there is no need to abort, + which is expensive. */ + __builtin_tend (); + /* Note: Changing the adapt_count here might abort a transaction on a + different cpu, but that could happen anyway when the futex is + acquired, so there's no need to check the nesting depth here. */ + if (aconf.skip_lock_busy > 0) + *adapt_count = aconf.skip_lock_busy; + } + else + { + if (status != _HTM_TBEGIN_TRANSIENT) + { + /* A persistent abort (cc 1 or 3) indicates that a retry is + probably futile. Use the normal locking now and for the + next couple of calls. + Be careful to avoid writing to the lock. */ + if (aconf.skip_trylock_internal_abort > 0) + *adapt_count = aconf.skip_trylock_internal_abort; + } + } + /* Could do some retries here. */ + } + else + { + /* Lost updates are possible, but harmless. Due to races this might lead + to *adapt_count becoming less than zero. */ + (*adapt_count)--; + } + + return lll_trylock (*futex); +} |