fix raise semantics with threads.

diff --git a/src/signal/raise.c b/src/signal/raise.c
index 52f8b42..f437d23 100644 (file)
--- a/src/signal/raise.c
+++ b/src/signal/raise.c
@@ -1,7 +1,18 @@
 #include <signal.h>
+#include <errno.h>
 #include "syscall.h"
 
 int raise(int sig)
 {
-       return __syscall_kill(__syscall_getpid(), sig);
+       int pid, tid, ret;
+       /* Getting the pid/tid pair is not atomic, and could give wrong
+        * result if a fork occurs in a signal handler between the two
+        * syscalls. Use the tgkill syscall's ESRCH semantics to detect
+        * this condition and retry. */
+       do {
+               tid = syscall0(__NR_gettid);
+               pid = syscall0(__NR_getpid);
+               ret = syscall3(__NR_tgkill, pid, tid, sig);
+       } while (ret<0 && errno == ESRCH);
+       return ret;
 }