From: Christian Babeux <christian.babeux@efficios.com>
Date: Wed, 28 Nov 2012 03:27:56 +0000 (-0500)
Subject: Cygwin: sigtimedwait workaround for SIGPIPE handling on wait pipe write
X-Git-Url: http://git.lttng.org/?p=lttng-ust.git;a=commitdiff_plain;h=8a9f3798dd0442b480d3b3371bc0278f897c12c8

Cygwin: sigtimedwait workaround for SIGPIPE handling on wait pipe write

sigtimedwait(3) is not available in Cygwin. To workaround
this limitation, if a SIGPIPE is pending after a write(3),
kill ourselve with SIGPIPE and use sigwaitinfo(3) to wait
on delivery and effectively "discarding" the signal.
---

diff --git a/libringbuffer/frontend_internal.h b/libringbuffer/frontend_internal.h
index 2d3b1071..9ff28e39 100644
--- a/libringbuffer/frontend_internal.h
+++ b/libringbuffer/frontend_internal.h
@@ -457,11 +457,20 @@ void lib_ring_buffer_check_deliver(const struct lttng_ust_lib_ring_buffer_config
 						ret = write(wakeup_fd, "", 1);
 					} while (ret == -1L && errno == EINTR);
 					if (ret == -1L && errno == EPIPE && !sigpipe_was_pending) {
-						struct timespec timeout = { 0, 0 };
-						do {
-							ret = sigtimedwait(&sigpipe_set, NULL,
-								&timeout);
-						} while (ret == -1L && errno == EINTR);
+						ret = sigpending(&pending_set);
+						assert(!ret);
+
+						if (sigismember(&pending_set, SIGPIPE)) {
+							/*
+							 * Kill ourselves with SIGPIPE and wait on
+							 * delivery, thus effectively discarding it.
+							 */
+							pthread_t self = pthread_self();
+							pthread_kill(self, SIGPIPE);
+							do {
+								ret = sigwaitinfo(&sigpipe_set, NULL);
+							} while (ret == -1L && errno == EINTR);
+						}
 					}
 					if (!sigpipe_was_pending) {
 						ret = pthread_sigmask(SIG_SETMASK, &old_set, NULL);