linux-kernel - [RFC,PATCH 02/14] signals: check ->group_stop_count after tracehook_get

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Message-ID: <20091124200135.GA5761@redhat.com>
Date:	Tue, 24 Nov 2009 21:01:35 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Alexey Dobriyan <adobriyan@...il.com>,
	Ananth Mavinakayanahalli <ananth@...ibm.com>,
	Christoph Hellwig <hch@...radead.org>,
	"Frank Ch. Eigler" <fche@...hat.com>, Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	Roland McGrath <roland@...hat.com>
Cc:	linux-kernel@...r.kernel.org, utrace-devel@...hat.com
Subject: [RFC,PATCH 02/14] signals: check ->group_stop_count after
	tracehook_get_signal()

(already in mm: signals-check-group_stop_count-after-tracehook_get_signal.patch)

Move the call to do_signal_stop() down, after tracehook call.
This makes ->group_stop_count condition visible to tracers before
do_signal_stop() will participate in this group-stop.

Currently the patch has no effect, tracehook_get_signal() always
returns 0.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
Acked-by: Roland McGrath <roland@...hat.com>
---

 kernel/signal.c |    9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

--- V1/kernel/signal.c~2_DO_SIGNAL_STOP_AFTER_TRACEHOOK	2009-11-24 19:46:51.000000000 +0100
+++ V1/kernel/signal.c	2009-11-24 19:51:13.000000000 +0100
@@ -1807,11 +1807,6 @@ relock:
 
 	for (;;) {
 		struct k_sigaction *ka;
-
-		if (unlikely(signal->group_stop_count > 0) &&
-		    do_signal_stop(0))
-			goto relock;
-
 		/*
 		 * Tracing can induce an artifical signal and choose sigaction.
 		 * The return value in @signr determines the default action,
@@ -1823,6 +1818,10 @@ relock:
 		if (unlikely(signr != 0))
 			ka = return_ka;
 		else {
+			if (unlikely(signal->group_stop_count > 0) &&
+			    do_signal_stop(0))
+				goto relock;
+
 			signr = dequeue_signal(current, &current->blocked,
 					       info);
 

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