make the modifySemaphore() signal-safe on linux

as POSIX man says, if semop() is interrupted by a signal,
it shall return -1 and set errno to EINTR.
in qcore_unix_p.h, we have EINTR_LOOP helper macro exactly for such cases ;)

Task-number: QTBUG-14434
Merge-request: 998
Reviewed-by: Olivier Goffart

1 files changed, 6 insertions, 1 deletions

diff --git a/src/corelib/kernel/qsystemsemaphore_unix.cpp b/src/corelib/kernel/qsystemsemaphore_unix.cpp
index e76331e..7e45497 100644
--- a/src/corelib/kernel/qsystemsemaphore_unix.cpp
+++ b/src/corelib/kernel/qsystemsemaphore_unix.cpp
@@ -56,6 +56,8 @@
 
 #include <sys/sem.h>
 
+#include "private/qcore_unix_p.h"
+
 // OpenBSD 4.2 doesn't define EIDRM, see BUGS section:
 // http://www.openbsd.org/cgi-bin/man.cgi?query=semop&manpath=OpenBSD+4.2
 #if defined(Q_OS_OPENBSD) && !defined(EIDRM)
@@ -218,7 +220,10 @@ bool QSystemSemaphorePrivate::modifySemaphore(int count)
     operation.sem_num = 0;
     operation.sem_op = count;
     operation.sem_flg = SEM_UNDO;
-    if (-1 == semop(semaphore, &operation, 1)) {
+
+    register int res;
+    EINTR_LOOP(res, semop(semaphore, &operation, 1));
+    if (-1 == res) {
         // If the semaphore was removed be nice and create it and then modifySemaphore again
         if (errno == EINVAL || errno == EIDRM) {
             semaphore = -1;