commit 73c7f5a87971de2797f261e1a447f68dce09284b

Author: Florian Weimer <fweimer@redhat.com>

Date:   Mon Sep 20 14:56:08 2021 +0200

    nptl: pthread_kill needs to return ESRCH for old programs (bug 19193)

    The fix for bug 19193 breaks some old applications which appear

    to use pthread_kill to probe if a thread is still running, something

    that is not supported by POSIX.

    (cherry picked from commit 95dba35bf05e4a5d69dfae5e9c9d4df3646a7f93)

diff --git a/nptl/pthread_kill.c b/nptl/pthread_kill.c

index fb7862eff787a94f..a44dc8f2d9baa925 100644

--- a/nptl/pthread_kill.c

+++ b/nptl/pthread_kill.c

@@ -21,8 +21,11 @@

 #include <pthreadP.h>

 #include <shlib-compat.h>

-int

-__pthread_kill_internal (pthread_t threadid, int signo)

+/* Sends SIGNO to THREADID.  If the thread is about to exit or has

+   already exited on the kernel side, return NO_TID.  Otherwise return

+   0 or an error code. */

+static int

+__pthread_kill_implementation (pthread_t threadid, int signo, int no_tid)

 {

   struct pthread *pd = (struct pthread *) threadid;

   if (pd == THREAD_SELF)

@@ -52,11 +55,8 @@ __pthread_kill_internal (pthread_t threadid, int signo)

        signal is either not observable (the target thread has already

        blocked signals at this point), or it will fail, or it might be

        delivered to a new, unrelated thread that has reused the TID.

-       So do not actually send the signal.  Do not report an error

-       because the threadid argument is still valid (the thread ID

-       lifetime has not ended), and ESRCH (for example) would be

-       misleading.  */

-    ret = 0;

+       So do not actually send the signal.  */

+    ret = no_tid;

   else

     {

       /* Using tgkill is a safety measure.  pd->exit_lock ensures that

@@ -71,6 +71,15 @@ __pthread_kill_internal (pthread_t threadid, int signo)

   return ret;

 }

+int

+__pthread_kill_internal (pthread_t threadid, int signo)

+{

+  /* Do not report an error in the no-tid case because the threadid

+     argument is still valid (the thread ID lifetime has not ended),

+     and ESRCH (for example) would be misleading.  */

+  return __pthread_kill_implementation (threadid, signo, 0);

+}

+

 int

 __pthread_kill (pthread_t threadid, int signo)

 {

@@ -81,6 +90,7 @@ __pthread_kill (pthread_t threadid, int signo)

   return __pthread_kill_internal (threadid, signo);

 }

+

 /* Some architectures (for instance arm) might pull raise through libgcc, so

    avoid the symbol version if it ends up being used on ld.so.  */

 #if !IS_IN(rtld)

@@ -88,6 +98,17 @@ libc_hidden_def (__pthread_kill)

 versioned_symbol (libc, __pthread_kill, pthread_kill, GLIBC_2_34);

 # if OTHER_SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_34)

-compat_symbol (libc, __pthread_kill, pthread_kill, GLIBC_2_0);

+/* Variant which returns ESRCH in the no-TID case, for backwards

+   compatibility.  */

+int

+attribute_compat_text_section

+__pthread_kill_esrch (pthread_t threadid, int signo)

+{

+  if (__is_internal_signal (signo))

+    return EINVAL;

+

+  return __pthread_kill_implementation (threadid, signo, ESRCH);

+}

+compat_symbol (libc, __pthread_kill_esrch, pthread_kill, GLIBC_2_0);

 # endif

 #endif

diff --git a/sysdeps/pthread/tst-pthread_kill-exited.c b/sysdeps/pthread/tst-pthread_kill-exited.c

index 7575fb6d58cae99c..a2fddad526666c8c 100644

--- a/sysdeps/pthread/tst-pthread_kill-exited.c

+++ b/sysdeps/pthread/tst-pthread_kill-exited.c

@@ -16,11 +16,15 @@

    License along with the GNU C Library; if not, see

    <https://www.gnu.org/licenses/>.  */

-/* This test verifies that pthread_kill returns 0 (and not ESRCH) for

-   a thread that has exited on the kernel side.  */

+/* This test verifies that the default pthread_kill returns 0 (and not

+   ESRCH) for a thread that has exited on the kernel side.  */

+#include <errno.h>

+#include <pthread.h>

+#include <shlib-compat.h>

 #include <signal.h>

 #include <stddef.h>

+#include <support/check.h>

 #include <support/support.h>

 #include <support/xthread.h>

@@ -30,6 +34,12 @@ noop_thread (void *closure)

   return NULL;

 }

+#if TEST_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_34) && PTHREAD_IN_LIBC

+extern __typeof (pthread_kill) compat_pthread_kill;

+compat_symbol_reference (libpthread, compat_pthread_kill, pthread_kill,

+                         GLIBC_2_0);

+#endif

+

 static int

 do_test (void)

 {

@@ -37,7 +47,14 @@ do_test (void)

   support_wait_for_thread_exit ();

+  /* NB: Always uses the default symbol due to separate compilation.  */

   xpthread_kill (thr, SIGUSR1);

+

+#if TEST_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_34) && PTHREAD_IN_LIBC

+  /* Old binaries need the non-conforming ESRCH error code.  */

+  TEST_COMPARE (compat_pthread_kill (thr, SIGUSR1), ESRCH);

+#endif

+

   xpthread_join (thr);

   return 0;