linux-kernel - [PATCH] livepatch: Replace the fake signal sending with TIF_NOTIFY

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Message-Id: <20210326143021.17773-1-mbenes@suse.cz>
Date:   Fri, 26 Mar 2021 15:30:21 +0100
From:   Miroslav Benes <mbenes@...e.cz>
To:     jpoimboe@...hat.com, jikos@...nel.org, pmladek@...e.com,
        joe.lawrence@...hat.com
Cc:     live-patching@...r.kernel.org, linux-kernel@...r.kernel.org,
        axboe@...nel.dk, Miroslav Benes <mbenes@...e.cz>
Subject: [PATCH] livepatch: Replace the fake signal sending with TIF_NOTIFY_SIGNAL infrastructure

Livepatch sends a fake signal to all remaining blocking tasks of a
running transition after a set period of time. It uses TIF_SIGPENDING
flag for the purpose. Commit 12db8b690010 ("entry: Add support for
TIF_NOTIFY_SIGNAL") added a generic infrastructure to achieve the same.
Replace our bespoke solution with the generic one.

Signed-off-by: Miroslav Benes <mbenes@...e.cz>
---
Tested on x86_64, s390x and ppc64le archs.

 kernel/livepatch/transition.c | 5 ++---
 kernel/signal.c               | 3 +--
 2 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/kernel/livepatch/transition.c b/kernel/livepatch/transition.c
index f6310f848f34..3a4beb9395c4 100644
--- a/kernel/livepatch/transition.c
+++ b/kernel/livepatch/transition.c
@@ -9,6 +9,7 @@
 
 #include <linux/cpu.h>
 #include <linux/stacktrace.h>
+#include <linux/tracehook.h>
 #include "core.h"
 #include "patch.h"
 #include "transition.h"
@@ -369,9 +370,7 @@ static void klp_send_signals(void)
 			 * Send fake signal to all non-kthread tasks which are
 			 * still not migrated.
 			 */
-			spin_lock_irq(&task->sighand->siglock);
-			signal_wake_up(task, 0);
-			spin_unlock_irq(&task->sighand->siglock);
+			set_notify_signal(task);
 		}
 	}
 	read_unlock(&tasklist_lock);
diff --git a/kernel/signal.c b/kernel/signal.c
index f2a1b898da29..e52cb82aaecd 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -181,8 +181,7 @@ void recalc_sigpending_and_wake(struct task_struct *t)
 
 void recalc_sigpending(void)
 {
-	if (!recalc_sigpending_tsk(current) && !freezing(current) &&
-	    !klp_patch_pending(current))
+	if (!recalc_sigpending_tsk(current) && !freezing(current))
 		clear_thread_flag(TIF_SIGPENDING);
 
 }
-- 
2.30.2