Package: libc6
Version: 2.3.2.ds1-13
Severity: normal
pthread_cond_timedwait with a timespec in the past sometimes destroys
the pthread_cond_t variable. The following pthread_cond_(timed)wait
calls ignore all signals on the condition variable and block.
There is no Workaround, because I cannot guarantee that the timespec is
really in the future (because the thread may be interrupted between
gettimeofday and pthread_cond_timedwait).
The problem only occurs with NPTL (i.e. I can't reproduce the problem
with LD_ASSUME_KERNEL=2.4.19).
The following program deadlocks after some iterations (10-1000).
*** /tmp/current/bug.c
// gcc -pthread -Wall -O2 -std=c99 bug.c -o bug
#include <stdio.h>
#include <pthread.h>
pthread_mutex_t mutex;
pthread_cond_t empty;
pthread_cond_t nonempty;
unsigned count = 0;
void* run(void* env)
{
pthread_mutex_lock(&mutex);
struct timespec ts = { 0, 0 };
for (;;) {
count = 0;
pthread_cond_signal(&empty);
pthread_cond_timedwait(&nonempty, &mutex, &ts);
count = 0;
pthread_cond_signal(&empty);
pthread_cond_wait(&nonempty, &mutex);
}
}
int main()
{
pthread_mutex_init(&mutex, 0);
pthread_cond_init(&empty, 0);
pthread_cond_init(&nonempty, 0);
pthread_t thread;
pthread_create(&thread, 0, &run, 0);
pthread_mutex_lock(&mutex);
for (unsigned i = 0;; ++i) {
while (count > 0) {
pthread_cond_wait(&empty, &mutex);
}
++count;
pthread_cond_signal(&nonempty);
printf("%u\n", i);
}
}
-- System Information:
Debian Release: testing/unstable
APT prefers unstable
APT policy: (500, 'unstable')
Architecture: i386 (i686)
Kernel: Linux 2.6.7-1-686-smp
Locale: LANG=C, [EMAIL PROTECTED]
Versions of packages libc6 depends on:
ii libdb1-compat 2.1.3-7 The Berkeley database routines [gl
-- no debconf information
--
To UNSUBSCRIBE, email to [EMAIL PROTECTED]
with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
