From 6ae1be1a121b9367ea11ce1789d99ec56fb39682 Mon Sep 17 00:00:00 2001 From: Martin Sustrik Date: Sun, 3 Jul 2011 15:30:31 +0200 Subject: Race condition in eventfd signaler fixed recv function on eventfd signaler could accidentally grab two signals instead of one. Fixed. Signed-off-by: Martin Sustrik --- src/signaler.cpp | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) (limited to 'src') diff --git a/src/signaler.cpp b/src/signaler.cpp index 3045467..fb72a07 100644 --- a/src/signaler.cpp +++ b/src/signaler.cpp @@ -206,8 +206,16 @@ void zmq::signaler_t::recv () uint64_t dummy; ssize_t sz = read (r, &dummy, sizeof (dummy)); errno_assert (sz == sizeof (dummy)); -if (dummy != 1) -printf ("dummy:%d\n", (int) dummy); + + // If we accidentally grabbed the next signal along with the current + // one, return it back to the eventfd object. + if (unlikely (dummy == 2)) { + const uint64_t inc = 1; + ssize_t sz = write (w, &inc, sizeof (inc)); + errno_assert (sz == sizeof (inc)); + return; + } + zmq_assert (dummy == 1); #else unsigned char dummy; -- cgit v1.2.3