[PATCH v2 17/19] nptl: Use tidlock when accessing TID on pthread_sigqueue

[Adhemerval Zanella]

Checked on x86_64-linux-gnu.
---
 nptl/pthread_sigqueue.c | 52 +++++++++++++++++++++--------------------
 1 file changed, 27 insertions(+), 25 deletions(-)

diff --git a/nptl/pthread_sigqueue.c b/nptl/pthread_sigqueue.c
index 2a0467ad7a..731e83884d 100644
--- a/nptl/pthread_sigqueue.c
+++ b/nptl/pthread_sigqueue.c
@@ -28,41 +28,43 @@
 int
 __pthread_sigqueue (pthread_t threadid, int signo, const union sigval value)
 {
-#ifdef __NR_rt_tgsigqueueinfo
   struct pthread *pd = (struct pthread *) threadid;
 
-  /* Force load of pd->tid into local variable or register.  Otherwise
-     if a thread exits between ESRCH test and tgkill, we might return
-     EINVAL, because pd->tid would be cleared by the kernel.  */
-  pid_t tid = atomic_forced_read (pd->tid);
-  if (__glibc_unlikely (tid <= 0))
-    /* Not a valid thread handle.  */
-    return ESRCH;
-
   /* Disallow sending the signal we use for cancellation, timers,
      for the setxid implementation.  */
   if (signo == SIGCANCEL || signo == SIGTIMER || signo == SIGSETXID)
     return EINVAL;
 
-  pid_t pid = getpid ();
+  /* Block all signal, since the lock is recursive and used on pthread_cancel
+     (which should be async-signal-safe).  */
+  sigset_t oldmask;
+  __libc_signal_block_all (&oldmask);
+  lll_lock (pd->tidlock, LLL_PRIVATE);
+
+  int res;
+  if (pd->tid == 0)
+    {
+      pid_t pid = getpid ();
 
-  /* Set up the siginfo_t structure.  */
-  siginfo_t info;
-  memset (&info, '\0', sizeof (siginfo_t));
-  info.si_signo = signo;
-  info.si_code = SI_QUEUE;
-  info.si_pid = pid;
-  info.si_uid = __getuid ();
-  info.si_value = value;
+      /* Set up the siginfo_t structure.  */
+      siginfo_t info;
+      memset (&info, '\0', sizeof (siginfo_t));
+      info.si_signo = signo;
+      info.si_code = SI_QUEUE;
+      info.si_pid = pid;
+      info.si_uid = __getuid ();
+      info.si_value = value;
 
-  /* We have a special syscall to do the work.  */
-  int val = INTERNAL_SYSCALL_CALL (rt_tgsigqueueinfo, pid, tid, signo,
+      res = INTERNAL_SYSCALL_CALL (rt_tgsigqueueinfo, pid, pd->tid, signo,
 				   &info);
-  return (INTERNAL_SYSCALL_ERROR_P (val)
-	  ? INTERNAL_SYSCALL_ERRNO (val) : 0);
-#else
-  return ENOSYS;
-#endif
+    }
+  else
+    res = -ESRCH;
+
+  lll_unlock (pd->tidlock, LLL_PRIVATE);
+  __libc_signal_restore_set (&oldmask);
+
+  return -res;
 }
 versioned_symbol (libc, __pthread_sigqueue, pthread_sigqueue, GLIBC_2_34);
 
-- 
2.30.2