nptl: Deallocate the thread stack on setup failure (BZ #19511)

To setup either the thread scheduling parameters or affinity,
pthread_create enforce synchronization on created thread to wait until
its parent either release PD ownership or send a cancellation signal if
a failure occurs.

However, cancelling the thread does not deallocate the newly created
stack since cancellation expects that a pthread_join to deallocate any
allocated thread resouces (threads stack or TLS).

This patch changes on how the thread resource is deallocate in case of
failure to be synchronous, where the creating thread will signal the
created thread to exit early so it could be joined.  The creating thread
will be reponsible for the resource cleanup before returning to the
caller.

To signal the creating thread that a failure has occured, an unused
'struct pthread' member, parent_cancelhandling_unsed, now indicates
whether the setup has failed so creating thread can proper exit.

This strategy also simplifies by not using thread cancellation and
thus not running libgcc_so load in the signal handler (which is
avoided in thread cancellation since 'pthread_cancel' is the one
responsible to dlopen libgcc_s).  Another advantage is since the
early exit is move to first step at thread creation, the signal
mask is not already set and thus it can not act on change ID setxid
handler.

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

1 files changed, 3 insertions, 2 deletions

diff --git a/nptl/descr.h b/nptl/descr.h
index 3de9535..9d8297b 100644
--- a/nptl/descr.h
+++ b/nptl/descr.h
@@ -340,8 +340,9 @@ struct pthread
   /* True if thread must stop at startup time.  */
   bool stopped_start;
 
-  /* Formerly used for dealing with cancellation.  */
-  int parent_cancelhandling_unsed;
+  /* Indicate that a thread creation setup has failed (for instance the
+     scheduler or affinity).  */
+  int setup_failed;
 
   /* Lock to synchronize access to the descriptor.  */
   int lock;