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.

1 files changed, 11 insertions, 12 deletions

diff --git a/nptl/tst-cancel13.c b/nptl/tst-cancel13.c
index c84780ded3..ee39b963ad 100644
--- a/nptl/tst-cancel13.c
+++ b/nptl/tst-cancel13.c
@@ -1,4 +1,5 @@
-/* Copyright (C) 2003-2016 Free Software Foundation, Inc.
+/* Test sem_wait cancellation for contended case.
+   Copyright (C) 2003-2016 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
    Contributed by Ulrich Drepper <drepper@redhat.com>, 2003.
 
@@ -39,8 +40,6 @@ cleanup (void *arg)
       puts ("second call to cleanup");
       exit (1);
     }
-
-  printf ("cleanup call #%d\n", ncall);
 }
 
 
@@ -52,7 +51,7 @@ 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);
     }
 
@@ -61,8 +60,6 @@ tf (void *arg)
 
   pthread_cleanup_pop (0);
 
-  puts ("sem_wait returned");
-
   return NULL;
 }
 
@@ -74,26 +71,28 @@ do_test (void)
 
   if (pthread_barrier_init (&bar, NULL, 2) != 0)
     {
-      puts ("barrier_init failed");
+      puts ("error: barrier_init failed");
       exit (1);
     }
 
+  /* A value equal to 0 will check for contended pthread cancellation,
+     where the sem_wait operation will block.  */
   if (sem_init (&sem, 0, 0) != 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);
     }
 
   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);
     }
 
@@ -103,14 +102,14 @@ do_test (void)
   /* Check whether cancellation is honored when waiting in sem_wait.  */
   if (pthread_cancel (th) != 0)
     {
-      puts ("1st cancel failed");
+      puts ("error: 1st cancel failed");
       exit (1);
     }
 
   void *r;
   if (pthread_join (th, &r) != 0)
     {
-      puts ("join failed");
+      puts ("error: join failed");
       exit (1);
     }