[PATCH v2 16/19] nptl: Use tidlock when accessing TID on pthread_setname_np

[Adhemerval Zanella via Libc-alpha <libc-alpha@sourceware.org>]

Checked on x86_64-linux-gnu.
---
 nptl/pthread_setname.c | 34 ++++++++++++++++++++++------------
 1 file changed, 22 insertions(+), 12 deletions(-)

diff --git a/nptl/pthread_setname.c b/nptl/pthread_setname.c
index 6d2d8a1723..0f541b4534 100644
--- a/nptl/pthread_setname.c
+++ b/nptl/pthread_setname.c
@@ -23,14 +23,14 @@
 #include <string.h>
 #include <unistd.h>
 #include <sys/prctl.h>
-
+#include <intprops.h>
 #include <not-cancel.h>
 
 
 int
 __pthread_setname_np (pthread_t th, const char *name)
 {
-  const struct pthread *pd = (const struct pthread *) th;
+  struct pthread *pd = (struct pthread *) th;
 
   /* Unfortunately the kernel headers do not export the TASK_COMM_LEN
      macro.  So we have to define it here.  */
@@ -42,23 +42,33 @@ __pthread_setname_np (pthread_t th, const char *name)
   if (pd == THREAD_SELF)
     return __prctl (PR_SET_NAME, name) ? errno : 0;
 
-#define FMT "/proc/self/task/%u/comm"
-  char fname[sizeof (FMT) + 8];
-  sprintf (fname, FMT, (unsigned int) pd->tid);
+  /* 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 fd = __open64_nocancel (fname, O_RDWR);
-  if (fd == -1)
-    return errno;
+  char fname[sizeof ("/proc/self/task//comm" ) + INT_BUFSIZE_BOUND (pid_t)];
+  __snprintf (fname, sizeof (fname), "/proc/self/task/%d/comm", pd->tid);
 
   int res = 0;
-  ssize_t n = TEMP_FAILURE_RETRY (__write_nocancel (fd, name, name_len));
-  if (n < 0)
+  int fd = __open64_nocancel (fname, O_RDWR);
+  if (fd == -1)
+    {
+      ssize_t n = TEMP_FAILURE_RETRY (__write_nocancel (fd, name, name_len));
+      if (n < 0)
+	res = errno;
+      else if (n != name_len)
+	res = EIO;
+    }
+  else
     res = errno;
-  else if (n != name_len)
-    res = EIO;
 
   __close_nocancel_nostatus (fd);
 
+  lll_unlock (pd->tidlock, LLL_PRIVATE);
+  __libc_signal_restore_set (&oldmask);
+
   return res;
 }
 versioned_symbol (libc, __pthread_setname_np, pthread_setname_np,
-- 
2.30.2