commit 18b3ffc1a8dc951d8a8cdb076e7e30aafc216571
Author: philippe <philippe@a5019735-40e9-0310-863c-91ae7b9d1cf9>
Date:   Sat Nov 19 14:54:44 2016 +0000

    Fix 372504  Hanging on exit_group
    
    Note that it is unclear if the PRE syscall for rt_sigsuspend
    is properly setting up a temporary mask in the thread state
    tmp_sig_mask:  if an handler is called while a thread is
    calling sigsuspend, the mask during the handler run must be
    the temporary mask set by sigsuspend.
    It is not clear if/where the valgrind sigframe builder/handler
    sets the tmp_sig_mask to the value as expected by the user
    (i.e. the value of the temporary mask which was given to
    the sigsuspend syscall)
    
    
    
    git-svn-id: svn://svn.valgrind.org/valgrind/trunk@16141 a5019735-40e9-0310-863c-91ae7b9d1cf9

diff --git a/coregrind/m_syswrap/syswrap-linux.c b/coregrind/m_syswrap/syswrap-linux.c
index 1dcb95d..fda8dd1 100644
--- a/coregrind/m_syswrap/syswrap-linux.c
+++ b/coregrind/m_syswrap/syswrap-linux.c
@@ -3558,6 +3558,12 @@ PRE(sys_rt_sigsuspend)
    PRE_REG_READ2(int, "rt_sigsuspend", vki_sigset_t *, mask, vki_size_t, size)
    if (ARG1 != (Addr)NULL) {
       PRE_MEM_READ( "rt_sigsuspend(mask)", ARG1, sizeof(vki_sigset_t) );
+      VG_(sigdelset)((vki_sigset_t*)ARG1, VG_SIGVGKILL); 
+      /* We cannot mask VG_SIGVGKILL, as otherwise this thread would not
+         be killable by VG_(nuke_all_threads_except).
+         We thus silently ignore the user request to mask this signal.
+         Note that this is similar to what is done for e.g.
+         sigprocmask (see m_signals.c calculate_SKSS_from_SCSS).  */
    }
 }
 
diff --git a/coregrind/pub_core_threadstate.h b/coregrind/pub_core_threadstate.h
index 861f233..f3d956c 100644
--- a/coregrind/pub_core_threadstate.h
+++ b/coregrind/pub_core_threadstate.h
@@ -354,7 +354,9 @@ typedef struct {
       different values is during the execution of a sigsuspend, where
       tmp_sig_mask is the temporary mask which sigsuspend installs.
       It is only consulted to compute the signal mask applied to a
-      signal handler. */
+      signal handler. 
+      PW Nov 2016 : it is not clear if and where this tmp_sig_mask
+      is set when an handler runs "inside" a sigsuspend. */
    vki_sigset_t tmp_sig_mask;
 
    /* A little signal queue for signals we can't get the kernel to