nptl: Use pthread_kill on pthread_cancel

It consolidates the tgkill call and it is the first step of making
pthread_cancel async-signal-safe.  It also fix a possible issue
where the 'struct pthread' tid is not read atomically, which might
send an invalid cancellation signal (similar to what
db988e50a87f613cb6b9e98a2fc66a4848bc3546 fixed for pthread_join).

Checked on x86_64-linux-gnu and aarch64-linux-gnu.

1 files changed, 1 insertions, 5 deletions

diff --git a/nptl/pthread_cancel.c b/nptl/pthread_cancel.c
index de4659a1f0..0698cd2046 100644
--- a/nptl/pthread_cancel.c
+++ b/nptl/pthread_cancel.c
@@ -110,11 +110,7 @@ __pthread_cancel (pthread_t th)
       return 0;
     }
 
-  pid_t pid = __getpid ();
-  int val = INTERNAL_SYSCALL_CALL (tgkill, pid, pd->tid, SIGCANCEL);
-  return INTERNAL_SYSCALL_ERROR_P (val)
-	 ? INTERNAL_SYSCALL_ERRNO (val)
-	 : 0;
+  return __pthread_kill_internal (th, SIGCANCEL);
 }
 versioned_symbol (libc, __pthread_cancel, pthread_cancel, GLIBC_2_34);