sigwait: Do not fail with EINTR and return error code [BZ #22478]

Since

commit 8b0e795aaa445e9167aa07b282c5720b35342c07
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date:   Wed Nov 1 11:49:05 2017 -0200

    Simplify Linux sig{timed}wait{info} implementations

sigwait can fail with EINTR.  Applications do not expect that, and the
error code is not documented in POSIX or the manual pages.

This commit restores the previous behavior by retrying the system call
on EINTR.  It also returns the error code, not -1, on the remaing
errors.

Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>

1 files changed, 9 insertions, 2 deletions

diff --git a/sysdeps/unix/sysv/linux/sigwait.c b/sysdeps/unix/sysv/linux/sigwait.c
index e6fb32a610..443c3ad8e1 100644
--- a/sysdeps/unix/sysv/linux/sigwait.c
+++ b/sysdeps/unix/sysv/linux/sigwait.c
@@ -17,13 +17,20 @@
 
 #include <signal.h>
 #include <sysdep-cancel.h>
+#include <errno.h>
 
 int
 __sigwait (const sigset_t *set, int *sig)
 {
   siginfo_t si;
-  if (__sigtimedwait (set, &si, 0) < 0)
-    return -1;
+  int ret;
+  do
+    ret = __sigtimedwait (set, &si, 0);
+  /* Applications do not expect sigwait to return with EINTR, and the
+     error code is not specified by POSIX.  */
+  while (ret < 0 && errno == EINTR);
+  if (ret < 0)
+    return errno;
   *sig = si.si_signo;
   return 0;
 }