From patchwork Thu Jul 30 16:48:56 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tulio Magno Quites Machado Filho X-Patchwork-Id: 7939 X-Patchwork-Delegate: carlos@redhat.com Received: (qmail 57365 invoked by alias); 30 Jul 2015 16:49:26 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Delivered-To: mailing list libc-alpha@sourceware.org Received: (qmail 57353 invoked by uid 89); 30 Jul 2015 16:49:25 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.9 required=5.0 tests=AWL, BAYES_50, KAM_LAZY_DOMAIN_SECURITY, RP_MATCHES_RCVD autolearn=ham version=3.3.2 X-HELO: e24smtp05.br.ibm.com X-MailFrom: tuliom@linux.vnet.ibm.com X-RcptTo: libc-alpha@sourceware.org From: "Tulio Magno Quites Machado Filho" To: libc-alpha@sourceware.org Cc: munroesj@linux.vnet.ibm.com Subject: [PATCH][BZ 18743] PowerPC: Fix a race condition when eliding a lock Date: Thu, 30 Jul 2015 13:48:56 -0300 Message-Id: <1438274936-26493-1-git-send-email-tuliom@linux.vnet.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15073016-0033-0000-0000-0000031E1DEA Note: this patch is updating the NEWS section of glibc 2.22 because that's the only one available right now. Whether this patch will end up in glibc 2.23 or 2.22 has to be defined. 8<---- The previous code used to evaluate the preprocessor token is_lock_free to a variable before starting a transaction. This behavior can cause an error if another thread got the lock (without using a transaction) between the conversion of the token and the beginning of the transaction. This patch delays the evaluation of is_lock_free to inside a transaction by moving this part of the code to the macro ELIDE_LOCK. 2015-07-30 Tulio Magno Quites Machado Filho [BZ #18743] * sysdeps/powerpc/nptl/elide.h (__elide_lock): Move most of this code to... (ELIDE_LOCK): ...here. (__get_new_count): New function with part of the code from __elide_lock that updates the value of adapt_count after a transaction abort. (__elided_trylock): Moved this code to... (ELIDE_TRYLOCK): ...here. --- NEWS | 2 +- sysdeps/powerpc/nptl/elide.h | 104 +++++++++++++++++++++---------------------- 2 files changed, 53 insertions(+), 53 deletions(-) diff --git a/NEWS b/NEWS index 5698310..92996d5 100644 --- a/NEWS +++ b/NEWS @@ -28,7 +28,7 @@ Version 2.22 18536, 18539, 18540, 18542, 18544, 18545, 18546, 18547, 18549, 18553, 18557, 18558, 18569, 18583, 18585, 18586, 18592, 18593, 18594, 18602, 18612, 18613, 18619, 18633, 18641, 18643, 18648, 18657, 18676, 18694, - 18696. + 18696, 18743. * Cache information can be queried via sysconf() function on s390 e.g. with _SC_LEVEL1_ICACHE_SIZE as argument. diff --git a/sysdeps/powerpc/nptl/elide.h b/sysdeps/powerpc/nptl/elide.h index 389f5a5..1d04ee9 100644 --- a/sysdeps/powerpc/nptl/elide.h +++ b/sysdeps/powerpc/nptl/elide.h @@ -23,67 +23,67 @@ # include # include -/* Returns true if the lock defined by is_lock_free as elided. - ADAPT_COUNT is a pointer to per-lock state variable. */ - +/* Get the new value of adapt_count according to the elision + configurations. Returns true if the system should retry again or false + otherwise. */ static inline bool -__elide_lock (uint8_t *adapt_count, int is_lock_free) +__get_new_count (uint8_t *adapt_count) { - if (*adapt_count > 0) + /* A persistent failure indicates that a retry will probably + result in another failure. Use normal locking now and + for the next couple of calls. */ + if (_TEXASRU_FAILURE_PERSISTENT (__builtin_get_texasru ())) { - (*adapt_count)--; + if (__elision_aconf.skip_lock_internal_abort > 0) + *adapt_count = __elision_aconf.skip_lock_internal_abort; return false; } - - for (int i = __elision_aconf.try_tbegin; i > 0; i--) - { - if (__builtin_tbegin (0)) - { - if (is_lock_free) - return true; - /* Lock was busy. */ - __builtin_tabort (_ABORT_LOCK_BUSY); - } - else - { - /* A persistent failure indicates that a retry will probably - result in another failure. Use normal locking now and - for the next couple of calls. */ - if (_TEXASRU_FAILURE_PERSISTENT (__builtin_get_texasru ())) - { - if (__elision_aconf.skip_lock_internal_abort > 0) - *adapt_count = __elision_aconf.skip_lock_internal_abort; - break; - } - /* Same logic as above, but for a number of temporary failures in a - a row. */ - else if (__elision_aconf.skip_lock_out_of_tbegin_retries > 0 - && __elision_aconf.try_tbegin > 0) - *adapt_count = __elision_aconf.skip_lock_out_of_tbegin_retries; - } - } - - return false; + /* Same logic as above, but for a number of temporary failures in a + a row. */ + else if (__elision_aconf.skip_lock_out_of_tbegin_retries > 0 + && __elision_aconf.try_tbegin > 0) + *adapt_count = __elision_aconf.skip_lock_out_of_tbegin_retries; + return true; } -# define ELIDE_LOCK(adapt_count, is_lock_free) \ - __elide_lock (&(adapt_count), is_lock_free) - - -static inline bool -__elide_trylock (uint8_t *adapt_count, int is_lock_free, int write) -{ - if (__elision_aconf.try_tbegin > 0) - { - if (write) - __builtin_tabort (_ABORT_NESTED_TRYLOCK); - return __elide_lock (adapt_count, is_lock_free); - } - return false; -} +/* Returns 0 if the lock defined by is_lock_free was elided. + ADAPT_COUNT is a per-lock state variable. */ +# define ELIDE_LOCK(adapt_count, is_lock_free) \ + ({ \ + int ret = 0; \ + if (adapt_count > 0) \ + (adapt_count)--; \ + else \ + for (int i = __elision_aconf.try_tbegin; i > 0; i--) \ + { \ + asm volatile("" ::: "memory"); \ + if (__builtin_tbegin (0)) \ + { \ + if (is_lock_free) \ + { \ + ret = 1; \ + break; \ + } \ + __builtin_tabort (_ABORT_LOCK_BUSY); \ + } \ + else \ + if (!__get_new_count(&adapt_count)) \ + break; \ + } \ + ret; \ + }) # define ELIDE_TRYLOCK(adapt_count, is_lock_free, write) \ - __elide_trylock (&(adapt_count), is_lock_free, write) + ({ \ + int ret = 0; \ + if (__elision_aconf.try_tbegin > 0) \ + { \ + if (write) \ + __builtin_tabort (_ABORT_NESTED_TRYLOCK); \ + ret = ELIDE_LOCK (adapt_count, is_lock_free); \ + } \ + ret; \ + }) static inline bool