From 47677f2edc815e85d0383a89b09733e95e5d7302 Mon Sep 17 00:00:00 2001 From: Adhemerval Zanella Date: Mon, 22 Aug 2016 09:39:46 -0300 Subject: nptl: Fix sem_wait and sem_timedwait cancellation (BZ#18243) This patch fixes both sem_wait and sem_timedwait cancellation point for uncontended case. In this scenario only atomics are involved and thus the futex cancellable call is not issue and a pending cancellation signal is not handled. The fix is straighforward by calling pthread_testcancel is both function start. Although it would be simpler to call CANCELLATION_P directly, I decided to add an internal pthread_testcancel alias and use it to export less internal implementation on such function. A possible change on how pthread_testcancel is internally implemented would lead to either continue to force use CANCELLATION_P or to adjust its every use. GLIBC testcase also does have tests for uncontended cases, test-cancel12 and test-cancel14.c, however both are flawed by adding another cancellation point just after thread pthread_cleanup_pop: 47 static void * 48 tf (void *arg) 49 { 50 pthread_cleanup_push (cleanup, NULL); 51 52 int e = pthread_barrier_wait (&bar); 53 if (e != 0 && e != PTHREAD_BARRIER_SERIAL_THREAD) 54 { 55 puts ("tf: 1st barrier_wait failed"); 56 exit (1); 57 } 58 59 /* This call should block and be cancelable. */ 60 sem_wait (&sem); 61 62 pthread_cleanup_pop (0); 63 64 puts ("sem_wait returned"); 65 66 return NULL; 67 } So sem_{timed}wait does not act on cancellation, pthread_cleanup_pop executes 'cleanup' and then 'puts' acts on cancellation. Since pthread_cleanup_pop removed the clean-up handler, it will ran only once and thus it won't accuse an error to indicate sem_wait has not acted on the cancellation signal. This patch also fixes this behavior by removing the cancellation point 'puts'. It also adds some cleanup on all sem_{timed}wait cancel tests. It partially fixes BZ #18243. Checked on x86_64. [BZ #18243] * nptl/pthreadP.h (__pthread_testcancel): Add prototype and hidden_proto. * nptl/pthread_testcancel.c (pthread_cancel): Add internal aliais definition. * nptl/sem_timedwait.c (sem_timedwait): Add cancellation check for uncontended case. * nptl/sem_wait.c (__new_sem_wait): Likewise. * nptl/tst-cancel12.c (cleanup): Remove wrong cancellation point. (tf): Fix check for uncontended case. (do_test): Likewise. * nptl/tst-cancel13.c (cleanup): Remove wrong cancellation point. (tf): Fix check for uncontended case. (do_test): Likewise. * nptl/tst-cancel14.c (cleanup): Remove wrong cancellation point. (tf): Fix check for uncontended case. (do_test): Likewise. * nptl/tst-cancel15.c (cleanup): Remove wrong cancellation point. (tf): Fix check for uncontended case. (do_test): Likewise. --- nptl/tst-cancel12.c | 29 +++++++++++++---------------- 1 file changed, 13 insertions(+), 16 deletions(-) (limited to 'nptl/tst-cancel12.c') diff --git a/nptl/tst-cancel12.c b/nptl/tst-cancel12.c index ac8f5a0559..a720ccfaf0 100644 --- a/nptl/tst-cancel12.c +++ b/nptl/tst-cancel12.c @@ -1,4 +1,5 @@ -/* Copyright (C) 2003-2016 Free Software Foundation, Inc. +/* Test sem_wait cancellation for uncontended case. + Copyright (C) 2003-2016 Free Software Foundation, Inc. This file is part of the GNU C Library. Contributed by Ulrich Drepper , 2003. @@ -39,8 +40,6 @@ cleanup (void *arg) puts ("second call to cleanup"); exit (1); } - - printf ("cleanup call #%d\n", ncall); } @@ -52,17 +51,15 @@ tf (void *arg) int e = pthread_barrier_wait (&bar); if (e != 0 && e != PTHREAD_BARRIER_SERIAL_THREAD) { - puts ("tf: 1st barrier_wait failed"); + puts ("error: tf: 1st barrier_wait failed"); exit (1); } - /* This call should block and be cancelable. */ + /* This call should be cancelable. */ sem_wait (&sem); pthread_cleanup_pop (0); - puts ("sem_wait returned"); - return NULL; } @@ -74,47 +71,47 @@ do_test (void) if (pthread_barrier_init (&bar, NULL, 2) != 0) { - puts ("barrier_init failed"); + puts ("error: barrier_init failed"); exit (1); } + /* A value higher than 0 will check for uncontended pthread cancellation, + where the sem_wait operation will return immediatelly. */ if (sem_init (&sem, 0, 1) != 0) { - puts ("sem_init failed"); + puts ("error: sem_init failed"); exit (1); } if (pthread_create (&th, NULL, tf, NULL) != 0) { - puts ("create failed"); + puts ("error: create failed"); exit (1); } - /* Check whether cancellation is honored even before sem_wait does - anything. */ if (pthread_cancel (th) != 0) { - puts ("1st cancel failed"); + puts ("error: pthread_cancel failed"); exit (1); } int e = pthread_barrier_wait (&bar); if (e != 0 && e != PTHREAD_BARRIER_SERIAL_THREAD) { - puts ("1st barrier_wait failed"); + puts ("error: 1st barrier_wait failed"); exit (1); } void *r; if (pthread_join (th, &r) != 0) { - puts ("join failed"); + puts ("error: pthread_join failed"); exit (1); } if (r != PTHREAD_CANCELED) { - puts ("thread not canceled"); + puts ("error: thread not canceled"); exit (1); } -- cgit 1.4.1