From 8af8456004edbab71f8903a60a3cae442cf6fe69 Mon Sep 17 00:00:00 2001 From: Florian Weimer Date: Mon, 13 Sep 2021 11:06:08 +0200 Subject: nptl: pthread_kill, pthread_cancel should not fail after exit (bug 19193) This closes one remaining race condition related to bug 12889: if the thread already exited on the kernel side, returning ESRCH is not correct because that error is reserved for the thread IDs (pthread_t values) whose lifetime has ended. In case of a kernel-side exit and a valid thread ID, no signal needs to be sent and cancellation does not have an effect, so just return 0. sysdeps/pthread/tst-kill4.c triggers undefined behavior and is removed with this commit. Reviewed-by: Adhemerval Zanella --- nptl/pthread_cancel.c | 9 +++++---- nptl/pthread_kill.c | 7 ++++++- 2 files changed, 11 insertions(+), 5 deletions(-) (limited to 'nptl') diff --git a/nptl/pthread_cancel.c b/nptl/pthread_cancel.c index 2bb523c0ec..a8aa3b3d15 100644 --- a/nptl/pthread_cancel.c +++ b/nptl/pthread_cancel.c @@ -61,10 +61,11 @@ __pthread_cancel (pthread_t th) { volatile struct pthread *pd = (volatile struct pthread *) th; - /* Make sure the descriptor is valid. */ - if (INVALID_TD_P (pd)) - /* Not a valid thread handle. */ - return ESRCH; + if (pd->tid == 0) + /* The thread has already exited on the kernel side. Its outcome + (regular exit, other cancelation) has already been + determined. */ + return 0; static int init_sigcancel = 0; if (atomic_load_relaxed (&init_sigcancel) == 0) diff --git a/nptl/pthread_kill.c b/nptl/pthread_kill.c index f79a2b26fc..5d4c86f920 100644 --- a/nptl/pthread_kill.c +++ b/nptl/pthread_kill.c @@ -46,7 +46,12 @@ __pthread_kill_internal (pthread_t threadid, int signo) ? INTERNAL_SYSCALL_ERRNO (val) : 0); } else - val = ESRCH; + /* The kernel reports that the thread has exited. POSIX specifies + the ESRCH error only for the case when the lifetime of a thread + ID has ended, but calling pthread_kill on such a thread ID is + undefined in glibc. Therefore, do not treat kernel thread exit + as an error. */ + val = 0; return val; } -- cgit 1.4.1