[Qemu-devel] [PATCH] Fix signal handling of SIG_IPI when io-thread is enabled

[Alexandre Raymond <cerbere@gmail.com>]

Both the signal thread (via sigwait()) and the cpu thread (via
a normal signal handler) were attempting to catch SIG_IPI.

This resulted in random freezes under Darwin.

This patch separates SIG_IPI from the rest of the signals handled
by the signal thread, because it is independently caught by the cpu
thread.

Signed-off-by: Alexandre Raymond <cerbere@gmail.com>
---
 cpus.c |   10 +++++++++-
 1 files changed, 9 insertions(+), 1 deletions(-)

diff --git a/cpus.c b/cpus.c
index 18a1522..84ffd1c 100644
--- a/cpus.c
+++ b/cpus.c
@@ -394,10 +394,18 @@ static int qemu_signal_init(void)
     sigaddset(&set, SIGUSR2);
     pthread_sigmask(SIG_UNBLOCK, &set, NULL);
 
+    /*
+     * SIG_IPI must be blocked in the main thread and must not be caught
+     * by sigwait() in the signal thread. Otherwise, the cpu thread will
+     * not catch it reliably.
+     */
+    sigemptyset(&set);
+    sigaddset(&set, SIG_IPI);
+    pthread_sigmask(SIG_BLOCK, &set, NULL);
+
     sigemptyset(&set);
     sigaddset(&set, SIGIO);
     sigaddset(&set, SIGALRM);
-    sigaddset(&set, SIG_IPI);
     sigaddset(&set, SIGBUS);
 #else
     sigemptyset(&set);
-- 
1.7.5