Re: [PATCH 3/5] Linux waitpid/__WALL emulation wrapper: If WNOHANG is set, don't touch sigprocmask.

[Pedro Alves <palves at redhat dot com>]

On 01/23/2014 02:10 PM, Pedro Alves wrote:
> So the caller can use waitpid WNOHANG+sigsuspend.  Otherwise,
> my_waitpid lets the SIGCHLD handler run by mistake.

Sorry, that rationale was bogus.  I've pushed this in, but
as an optimization.

---
[PATCH] Linux waitpid/__WALL emulation wrapper: If WNOHANG is set,
 don't touch sigprocmask.

Just a small optimization.  No need to block/unblock signals if we're
not going to call sigsuspend.

gdb/
2014-02-27  Pedro Alves  <palves@redhat.com>

	* nat/linux-waitpid.c (my_waitpid): Only block signals if WNOHANG
	isn't set.
---
 gdb/ChangeLog           |  5 +++++
 gdb/nat/linux-waitpid.c | 21 +++++++++++++--------
 2 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index bb5f5aa..6cfb9c5 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,10 @@
 2014-02-27  Pedro Alves  <palves@redhat.com>
 
+	* nat/linux-waitpid.c (my_waitpid): Only block signals if WNOHANG
+	isn't set.
+
+2014-02-27  Pedro Alves  <palves@redhat.com>
+
 	PR 12702
 	* linux-nat.c (status_to_str): Moved to nat/linux-waitpid.c.
 	* nat/linux-waitpid.c: Include string.h.
diff --git a/gdb/nat/linux-waitpid.c b/gdb/nat/linux-waitpid.c
index e9e69db..4693120 100644
--- a/gdb/nat/linux-waitpid.c
+++ b/gdb/nat/linux-waitpid.c
@@ -92,15 +92,19 @@ my_waitpid (int pid, int *status, int flags)
 
       wnohang = (flags & WNOHANG) != 0;
       flags &= ~(__WALL | __WCLONE);
-      flags |= WNOHANG;
 
-      /* Block all signals while here.  This avoids knowing about
-	 LinuxThread's signals.  */
-      sigfillset (&block_mask);
-      sigprocmask (SIG_BLOCK, &block_mask, &org_mask);
+      if (!wnohang)
+	{
+	  flags |= WNOHANG;
+
+	  /* Block all signals while here.  This avoids knowing about
+	     LinuxThread's signals.  */
+	  sigfillset (&block_mask);
+	  sigprocmask (SIG_BLOCK, &block_mask, &org_mask);
 
-      /* ... except during the sigsuspend below.  */
-      sigemptyset (&wake_mask);
+	  /* ... except during the sigsuspend below.  */
+	  sigemptyset (&wake_mask);
+	}
 
       while (1)
 	{
@@ -129,7 +133,8 @@ my_waitpid (int pid, int *status, int flags)
 	  flags ^= __WCLONE;
 	}
 
-      sigprocmask (SIG_SETMASK, &org_mask, NULL);
+      if (!wnohang)
+	sigprocmask (SIG_SETMASK, &org_mask, NULL);
     }
   else
     {
-- 
1.7.11.7