Make pthread_getspecific async-signal-safe

README.google

@@ -503,3 +503,7 @@ elf/dl-load.c
   For b/22641205, #include _itoa.h
   (ppluzhnikov, google-local)
 
+nptl/pthread_getspecific.c
+nptl/tst-key5.c
+  Fix for b/18722637 : make pthread_getspecific signal safe.
+  (ahh, google-local, proposed upstream)

nptl/Makefile

@@ -228,7 +228,7 @@ tests = tst-typesizes \
 	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-key1 tst-key2 tst-key3 tst-key4 \
+	tst-key1 tst-key2 tst-key3 tst-key4 tst-key5 \
 	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 \
 	tst-barrier1 tst-barrier2 tst-barrier3 tst-barrier4 \
@@ -609,6 +609,8 @@ $(objpfx)tst-execstack: $(libdl)
 $(objpfx)tst-execstack.out: $(objpfx)tst-execstack-mod.so
 LDFLAGS-tst-execstack = -Wl,-z,noexecstack
 
+LDFLAGS-tst-key5 = -lrt
+
 $(objpfx)tst-fini1mod.so: $(shared-thread-library)
 
 tst-stackguard1-ARGS = --command "$(host-test-program-cmd) --child"

nptl/pthread_getspecific.c

@@ -53,16 +53,10 @@ __pthread_getspecific (key)
       data = &level2[idx2nd];
     }
 
-  void *result = data->data;
-  if (result != NULL)
-    {
-      uintptr_t seq = data->seq;
+  if (__builtin_expect (data->seq != __pthread_keys[key].seq, 0))
+    return NULL;
 
-      if (__builtin_expect (seq != __pthread_keys[key].seq, 0))
-	result = data->data = NULL;
-    }
-
-  return result;
+  return data->data;
 }
 strong_alias (__pthread_getspecific, pthread_getspecific)
 hidden_def (__pthread_getspecific)

nptl/tst-key5.c

@@ -0,0 +1,77 @@
+/* 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 <unistd.h>
+#include <signal.h>
+#include <time.h>
+#include <assert.h>
+#include <string.h>
+#include <stdio.h>
+
+
+pthread_key_t key;
+void *value;
+size_t r;
+static void
+handler (int signo)
+{
+  void *ret = pthread_getspecific (key);
+  /* We race with the setspecific--either result is fine, just not junk. */
+  assert (ret == value || ret == NULL);
+  r++;
+}
+
+
+int
+do_test (void)
+{
+  struct sigaction sa;
+  memset (&sa, 0, sizeof (sa));
+  sa.sa_handler = handler;
+
+  assert (0 == sigaction (SIGUSR1, &sa, NULL));
+
+  timer_t timer;
+  struct sigevent sevp;
+  sevp.sigev_notify = SIGEV_SIGNAL;
+  sevp.sigev_signo = SIGUSR1;
+  assert (0 == timer_create(CLOCK_MONOTONIC, &sevp, &timer));
+  struct itimerspec spec;
+  spec.it_value.tv_sec = 0;
+  spec.it_value.tv_nsec = 500;
+  spec.it_interval = spec.it_value;
+  timer_settime(timer, 0, &spec, NULL);
+#define NITERS (1000 * 1000)
+  for (int i = 0; i < NITERS; ++i)
+    {
+      value = (void *)((intptr_t)i + 1);
+      assert (0 == pthread_key_create(&key, NULL));
+      assert (0 == pthread_setspecific(key, value));
+      if (value != pthread_getspecific(key))
+        {
+          printf ("Lost a value\n");
+          return 1;
+        }
+      assert (0 == pthread_key_delete(key));
+    }
+  timer_delete(timer);
+  return 0;
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"