If multiple threads are blocked in sigwait() for the same signal that does

not have a user-supplied signal handler, when a signal is delivered, one
thread will receive the signal, and then the code reverts to having no
signal handler for the signal.  This can leave the other sigwait()ing
threads stranded permanently if the signal is later ignored, or can result
in process termination when the process should have delivered the signal to
one of the threads in sigwait().

To fix this problem, maintain a count of sigwait()ers for each signal that
has no default signal handler.  Use the count to correctly install/uninstall
dummy signal handlers.

Reviewed by:	deischen

1 files changed, 3 insertions, 0 deletions

diff --git a/lib/libpthread/thread/thr_init.c b/lib/libpthread/thread/thr_init.c
index dd5f53f..8e13f90 100644
--- a/lib/libpthread/thread/thr_init.c
+++ b/lib/libpthread/thread/thr_init.c
@@ -277,6 +277,9 @@ _thread_init(void)
 				 */
 				PANIC("Cannot read signal handler info");
 			}
+
+			/* Initialize the SIG_DFL dummy handler count. */
+			_thread_dfl_count[i] = 0;
 		}
 
 		/*