Hi, as I found few months ago[1], when calling pthread_key_delete() all its values in threads are not removed; this, plus the the fact that deleted keys can be reused in pthread_key_create(), causes that in some occasions (i.e. when a new key is actually a reused one) there are the old thread specific data still available in threads which previously set some using the key prior of being deleted and reused again.
Attached there is a patch fixing this behaviour by cleaning up all the values of the key being deleted. It includes also a small test case. [1] http://www.gnu.org/software/hurd/open_issues/libpthread_pthread_key_create_reuse.html -- Pino Toscano
From 557337b9348f29b29acb4b226fd8ffddf5f22d30 Mon Sep 17 00:00:00 2001
From: Pino Toscano <toscano.p...@tiscali.it>
Date: Wed, 2 Nov 2011 17:38:46 +0100
Subject: [PATCH] Remove all the values when deleting a key
When deleting a key using `pthread_key_delete', delete all the values
associated to that key in all the threads available. Otherwise, the
key reuse in `pthread_key_create' can cause new keys to have thread
specific data of the previously used key with the same index.
Add a test for this case, which creates and deletes pairs of keys
checking that they have a NULL thread specific data after creation.
* sysdeps/hurd/pt-key-delete.c (pthread_key_delete): Remove all the
values of the key in all the threads.
* tests/Makefile (CHECK_SRC): Add test-17.c.
* tests/test-17.c: New file.
---
sysdeps/hurd/pt-key-delete.c | 19 ++++++++++++++
tests/Makefile | 2 +-
tests/test-17.c | 57 ++++++++++++++++++++++++++++++++++++++++++
3 files changed, 77 insertions(+), 1 deletions(-)
create mode 100644 tests/test-17.c
diff --git a/sysdeps/hurd/pt-key-delete.c b/sysdeps/hurd/pt-key-delete.c
index 2426bb1..9d88647 100644
--- a/sysdeps/hurd/pt-key-delete.c
+++ b/sysdeps/hurd/pt-key-delete.c
@@ -35,8 +35,27 @@ pthread_key_delete (pthread_key_t key)
err = EINVAL;
else
{
+ int i;
+
__pthread_key_destructors[key] = PTHREAD_KEY_INVALID;
__pthread_key_invalid_count ++;
+
+ pthread_rwlock_rdlock (&__pthread_threads_lock);
+ for (i = 0; i < __pthread_num_threads; ++i)
+ {
+ struct __pthread *t;
+
+ t = __pthread_threads[i];
+
+ if (t == NULL)
+ continue;
+
+ /* Just remove the key, no need to care whether it was
+ already there. */
+ if (t->thread_specifics)
+ hurd_ihash_remove (t->thread_specifics, key);
+ }
+ pthread_rwlock_unlock (&__pthread_threads_lock);
}
__pthread_mutex_unlock (&__pthread_key_lock);
diff --git a/tests/Makefile b/tests/Makefile
index 9509c95..4e2a4a8 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -4,7 +4,7 @@ LDLIBS = -lpthread
CHECK_SRC := test-1.c test-2.c test-3.c test-6.c test-7.c test-8.c \
test-9.c test-10.c test-11.c test-12.c test-13.c test-14.c \
- test-15.c test-16.c
+ test-15.c test-16.c test-17.c
CHECK_OBJS := $(addsuffix .o,$(basename $(notdir $(CHECK_SRC))))
CHECK_PROGS := $(basename $(notdir $(CHECK_SRC))) \
diff --git a/tests/test-17.c b/tests/test-17.c
new file mode 100644
index 0000000..a8bd150
--- /dev/null
+++ b/tests/test-17.c
@@ -0,0 +1,57 @@
+/* Test that the key reuse inside libpthread does not cause thread
+ specific values to persist. */
+
+#define _GNU_SOURCE 1
+
+#include <pthread.h>
+#include <stdio.h>
+#include <assert.h>
+#include <errno.h>
+
+void
+work (int iter)
+{
+ error_t err;
+ pthread_key_t key1;
+ pthread_key_t key2;
+ void *value1;
+ void *value2;
+
+ printf ("work/%d: start\n", iter);
+ err = pthread_key_create (&key1, NULL);
+ assert (err == 0);
+ err = pthread_key_create (&key2, NULL);
+ assert (err == 0);
+
+ value1 = pthread_getspecific (key1);
+ value2 = pthread_getspecific (key2);
+ printf ("work/%d: pre-setspecific: %p,%p\n", iter, value1, value2);
+ assert (value1 == NULL);
+ assert (value2 == NULL);
+ err = pthread_setspecific (key1, (void *)(0x100 + iter));
+ assert (err == 0);
+ err = pthread_setspecific (key2, (void *)(0x200 + iter));
+ assert (err == 0);
+
+ value1 = pthread_getspecific (key1);
+ value2 = pthread_getspecific (key2);
+ printf ("work/%d: post-setspecific: %p,%p\n", iter, value1, value2);
+ assert (value1 == (void *)(0x100 + iter));
+ assert (value2 == (void *)(0x200 + iter));
+
+ err = pthread_key_delete (key1);
+ assert (err == 0);
+ err = pthread_key_delete (key2);
+ assert (err == 0);
+}
+
+int
+main (int argc, char *argv[])
+{
+ int i;
+
+ for (i = 0; i < 8; ++i)
+ work (i + 1);
+
+ return 0;
+}
--
1.7.7
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