Package: libc6
Version: 2.3.6.ds1-11
Severity: normal
Hi,
I'm led to believe (from older libc docs that include POSIX threads)
that printf is a known cancellation point (albeit indirectly).
However, in practice it appears that if it is called with a cancellation
request pending it will deadlock... The following code reproduces this:
#define _REENTRANT 1
#include <pthread.h>
#include <stdio.h>
void *thread(void*)
{
printf("hello thread\n");
return NULL;
}
int main()
{
pthread_t id;
pthread_create(&id,NULL,thread,NULL);
pthread_cancel(id);
printf("joining thread\n");
pthread_join(id,NULL);
printf("done\n");
return 0;
}
$ g++ -g thread_join.cpp -o thread_join -pthread
$ ./thread_join
joining thread
<hang>
$ gdb ./thread_join 18867
(gdb) info threads
1 Thread 47608883437824 (LWP 18867) 0x00002b4cce7f530b in
__lll_mutex_lock_wait () from /lib/libc.so.6
(gdb) bt
#0 0x00002b4cce7f530b in __lll_mutex_lock_wait () from /lib/libc.so.6
#1 0x00002b4cce959090 in _IO_stdfile_0_lock () from /lib/libc.so.6
#2 0x0000000000000000 in ?? ()
Cheers,
Ron
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