Attachment 8326 Details for Bug 18435 – Proposed patch tested on powerpc64le and x86_64.

[patch] Proposed patch tested on powerpc64le and x86_64.

glibc-18435-pthread_once.patch (text/plain), 6.28 KB, created by Martin Sebor on 2015-05-20 00:09:43 UTC

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Creator: Martin Sebor

Created: 2015-05-20 00:09:43 UTC

Size: 6.28 KB

patch

obsolete

>diff --git a/ChangeLog b/ChangeLog
>index b7f3c61..943ce60 100644
>--- a/ChangeLog
>+++ b/ChangeLog
>@@ -1,3 +1,13 @@
>+2015-05-19  Martin Sebor  <msebor@redhat.com>
>+
>+	[BZ #18???]
>+	* nptl/ptherad_once (CleanupInfo): New struct.
>+	(clear_once_control): Replace...
>+	(cleanup_maybe_clear_once_control): ...with this.
>+	(__pthread_once_slow): Replace calls to pthread_cleanup_push and
>+	pthread_cleanup_pop with a cleanup object of struct CleanupInfo.
>+	* nptl/tst-once5.cc: New test.
>+
> 2015-05-18  Siddhesh Poyarekar  <siddhesh@redhat.com>
> 
> 	* .gitignore: Ignore generated *.pyc.
>diff --git a/nptl/Makefile b/nptl/Makefile
>index d784c8d..1bf35cb 100644
>--- a/nptl/Makefile
>+++ b/nptl/Makefile
>@@ -203,6 +203,7 @@ CFLAGS-send.c = -fexceptions -fasynchronous-unwind-tables
> 
> CFLAGS-pt-system.c = -fexceptions
> 
>+LDFLAGS-tst-once5 = -lstdc++
> 
> tests = tst-typesizes \
> 	tst-attr1 tst-attr2 tst-attr3 tst-default-attr \
>@@ -224,7 +225,7 @@ tests = tst-typesizes \
> 	tst-rwlock1 tst-rwlock2 tst-rwlock2a tst-rwlock3 tst-rwlock4 \
> 	tst-rwlock5 tst-rwlock6 tst-rwlock7 tst-rwlock8 tst-rwlock9 \
> 	tst-rwlock10 tst-rwlock11 tst-rwlock12 tst-rwlock13 tst-rwlock14 \
>-	tst-once1 tst-once2 tst-once3 tst-once4 \
>+	tst-once1 tst-once2 tst-once3 tst-once4 tst-once5 \
> 	tst-key1 tst-key2 tst-key3 tst-key4 \
> 	tst-sem1 tst-sem2 tst-sem3 tst-sem4 tst-sem5 tst-sem6 tst-sem7 \
> 	tst-sem8 tst-sem9 tst-sem10 tst-sem11 tst-sem12 tst-sem13 tst-sem14 \
>diff --git a/nptl/pthread_once.c b/nptl/pthread_once.c
>index fe6d923..8905b8f 100644
>--- a/nptl/pthread_once.c
>+++ b/nptl/pthread_once.c
>@@ -23,19 +23,24 @@
> 
> unsigned long int __fork_generation attribute_hidden;
> 
>+struct CleanupInfo {
>+  pthread_once_t *once;
>+};
> 
> static void
>-clear_once_control (void *arg)
>+cleanup_maybe_clear_once_control (struct CleanupInfo *pinfo)
> {
>-  pthread_once_t *once_control = (pthread_once_t *) arg;
>-
>-  /* Reset to the uninitialized state here.  We don't need a stronger memory
>-     order because we do not need to make any other of our writes visible to
>-     other threads that see this value: This function will be called if we
>-     get interrupted (see __pthread_once), so all we need to relay to other
>-     threads is the state being reset again.  */
>-  atomic_store_relaxed (once_control, 0);
>-  lll_futex_wake (once_control, INT_MAX, LLL_PRIVATE);
>+  if (pinfo->once) {
>+
>+    /* Reset the once control variable to the uninitialized state here.
>+       We don't need a stronger memory order because we do not need to
>+       make any other of our writes visible to other threads that see
>+       this value: This function will be called if we get interrupted
>+       (see __pthread_once), so all we need to relay to other threads
>+       is the state being reset again.  */
>+    atomic_store_relaxed (pinfo->once, 0);
>+    lll_futex_wake (pinfo->once, INT_MAX, LLL_PRIVATE);
>+  }
> }
> 
> 
>@@ -107,14 +112,18 @@ __pthread_once_slow (pthread_once_t *once_control, void (*init_routine) (void))
> 	}
> 
>       /* This thread is the first here.  Do the initialization.
>-	 Register a cleanup handler so that in case the thread gets
>-	 interrupted the initialization can be restarted.  */
>-      pthread_cleanup_push (clear_once_control, once_control);
>+         Register a cleanup handler so that in case the thread gets
>+         interrupted or the initialization routine exits by throwing
>+         an exception the initialization can be restarted.  */
> 
>-      init_routine ();
>+      struct CleanupInfo
>+        cleanupobj __attribute__ ((cleanup (cleanup_maybe_clear_once_control)))
>+        = { .once = once_control };
> 
>-      pthread_cleanup_pop (0);
>+      init_routine ();
> 
>+      /* Reset the once control variable to disable cleanup.  */
>+      cleanupobj.once = 0;
> 
>       /* Mark *once_control as having finished the initialization.  We need
>          release memory order here because we need to synchronize with other
>diff --git a/nptl/tst-once5.cc b/nptl/tst-once5.cc
>new file mode 100644
>index 0000000..60bc78a
>--- /dev/null
>+++ b/nptl/tst-once5.cc
>@@ -0,0 +1,80 @@
>+/* Copyright (C) 2015 Free Software Foundation, Inc.
>+   This file is part of the GNU C Library.
>+   Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
>+
>+   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 <errno.h>
>+#include <pthread.h>
>+#include <stdio.h>
>+#include <string.h>
>+
>+
>+static pthread_once_t once = PTHREAD_ONCE_INIT;
>+
>+// Exception type thrown from the pthread_once init routine.
>+struct OnceException { };
>+
>+// Test iteration counter.
>+static int niter;
>+
>+static void
>+init_routine (void)
>+{
>+  if (niter < 2)
>+    throw OnceException ();
>+}
>+
>+// Verify that an exception thrown from the pthread_once init routine
>+// is propagated to the pthread_once caller and that the function can
>+// be subsequently invoked to attempt the initialization again.
>+static int
>+do_test (void)
>+{
>+  int result = 1;
>+
>+  // Repeat three times, having the init routine throw the first two
>+  // times and succeed on the final attempt.
>+  for (niter = 0; niter != 3; ++niter) {
>+
>+    try {
>+      int rc = pthread_once (&once, init_routine);
>+      if (rc)
>+        fprintf (stderr, "pthread_once failed: %i (%s)\n",
>+                 rc, strerror (rc));
>+
>+      if (niter < 2)
>+        fputs ("pthread_once unexpectedly returned without"
>+               " throwing an exception", stderr);
>+    }
>+    catch (OnceException) {
>+      if (1 < niter)
>+        fputs ("pthread_once unexpectedly threw", stderr);
>+      result = 0;
>+    }
>+    catch (...) {
>+      fputs ("pthread_once threw an unknown exception", stderr);
>+    }
>+
>+    // Abort the test on the first failure.
>+    if (result)
>+      break;
>+  }
>+
>+  return result;
>+}
>+
>+#define TEST_FUNCTION do_test ()
>+#include "../test-skeleton.c"

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