The tst-cancel20 open two pipes and creates a thread which blocks
reading the first pipe. It then issues a signal to activate the
signal handler which in turn blocks reading the second pipe end.
Finally the cancellation cleanup-up handlers are tested by first
closing the all the pipes ends and issuing a pthread_cancel.
The tst-cancel21 have a similar behavior, but use an extra fork
after the test itself.
The race condition occurs if the cancellation handling acts after the
pipe close: in this case read will return EOF (indicating side-effects)
and thus the cancellation must not act. However current GLIBC
cancellation behavior acts regardless the syscalls returns with
sid-effects.
This patch adjust the test by moving the pipe closing after the
cancellation handling. This avoid spurious cancellation if the case
of the race described.
Checked on x86_64 and i386.
* nptl/tst-cancel20.c (do_one_test): Move the pipe closing after
pthread_join.
* nptl/tst-cancel21.c (tf): Likewise.
+2015-12-02 Adhemerval Zanella <adhemerval.zanella@linaro.org>
+
+ * nptl/tst-cancel20.c (do_one_test): Move the pipe closing after
+ pthread_join.
+ * nptl/tst-cancel21.c (tf): Likewise.
+
2015-12-01 H.J. Lu <hongjiu.lu@intel.com>
[BZ #19313]
return 1;
}
- /* This will cause the read in the child to return. */
- close (fd[0]);
- close (fd[1]);
- close (fd[2]);
- close (fd[3]);
-
void *ret;
if (pthread_join (th, &ret) != 0)
{
return 1;
}
+ /* The pipe closing must be issued after the cancellation handling to avoid
+ a race condition where the cancellation runs after both pipe ends are
+ closed. In this case the read syscall returns EOF and the cancellation
+ must not act. */
+ close (fd[0]);
+ close (fd[1]);
+ close (fd[2]);
+ close (fd[3]);
+
return 0;
}
exit (1);
}
- /* This will cause the read in the initial thread to return. */
- close (fd[0]);
- close (fd[1]);
- close (fd[2]);
- close (fd[3]);
-
void *ret;
if (pthread_join (th, &ret) != 0)
{
exit (1);
}
+ /* The pipe closing must be issued after the cancellation handling to avoid
+ a race condition where the cancellation runs after both pipe ends are
+ closed. In this case the read syscall returns EOF and the cancellation
+ must not act. */
+ close (fd[0]);
+ close (fd[1]);
+ close (fd[2]);
+ close (fd[3]);
+
exit (0);
}