[glibc] htl: Keep thread signals blocked during its initialization

[Samuel Thibault]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=d482ebfa67850976485fdf061cd52427eb8a3cb7

commit d482ebfa67850976485fdf061cd52427eb8a3cb7
Author: Samuel Thibault <samuel.thibault@ens-lyon.org>
Date:   Wed Nov 11 12:49:10 2020 +0000

    htl: Keep thread signals blocked during its initialization
    
    One may send signals immediately after creating a thread. We need to block them
    until the thread is ready to run signal handlers.

Diff:
---
 htl/pt-create.c   | 12 ++++++++++--
 htl/pt-internal.h |  3 +++
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/htl/pt-create.c b/htl/pt-create.c
index 7ac875cbf7..9364c40453 100644
--- a/htl/pt-create.c
+++ b/htl/pt-create.c
@@ -46,6 +46,8 @@ unsigned int __pthread_total;
 static void
 entry_point (struct __pthread *self, void *(*start_routine) (void *), void *arg)
 {
+  int err;
+
   ___pthread_self = self;
   __resp = &self->res_state;
 
@@ -60,6 +62,10 @@ entry_point (struct __pthread *self, void *(*start_routine) (void *), void *arg)
 
   __pthread_startup ();
 
+  /* We can now unleash signals.  */
+  err = __pthread_sigstate (self, SIG_SETMASK, &self->init_sigset, 0, 0);
+  assert_perror (err);
+
   if (self->c11)
     {
       /* The function pointer of the c11 thread start is cast to an incorrect
@@ -201,11 +207,13 @@ __pthread_create_internal (struct __pthread **thread,
      shall be empty."  If the currnet thread is not a pthread then we
      just inherit the process' sigmask.  */
   if (__pthread_num_threads == 1)
-    err = __sigprocmask (0, 0, &sigset);
+    err = __sigprocmask (0, 0, &pthread->init_sigset);
   else
-    err = __pthread_sigstate (_pthread_self (), 0, 0, &sigset, 0);
+    err = __pthread_sigstate (_pthread_self (), 0, 0, &pthread->init_sigset, 0);
   assert_perror (err);
 
+  /* But block the signals for now, until the thread is fully initialized.  */
+  __sigfillset (&sigset);
   err = __pthread_sigstate (pthread, SIG_SETMASK, &sigset, 0, 1);
   assert_perror (err);
 
diff --git a/htl/pt-internal.h b/htl/pt-internal.h
index e0baa6bcda..9dffa0e32e 100644
--- a/htl/pt-internal.h
+++ b/htl/pt-internal.h
@@ -102,6 +102,9 @@ struct __pthread
   /* Indicates whether is a C11 thread created by thrd_creat.  */
   bool c11;
 
+  /* Initial sigset for the thread.  */
+  sigset_t init_sigset;
+
   /* Thread context.  */
   struct pthread_mcontext mcontext;