linux-kernel - [PATCH] signal: Revert ptrace preempt magic

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Message-ID: <20180524143629.2ofsg7mhjixr5pnm@linutronix.de>
Date:   Thu, 24 May 2018 16:36:30 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     linux-kernel@...r.kernel.org
Cc:     Miklos Szeredi <mszeredi@...e.cz>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH] signal: Revert ptrace preempt magic

From: Thomas Gleixner <tglx@...utronix.de>

Upstream commit '53da1d9456fe7f8 fix ptrace slowness' is nothing more
than a bandaid around the ptrace design trainwreck. It's not a
correctness issue, it's merily a cosmetic bandaid.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
 kernel/signal.c |    8 --------
 1 file changed, 8 deletions(-)

--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1876,15 +1876,7 @@ static void ptrace_stop(int exit_code, i
 		if (gstop_done && ptrace_reparented(current))
 			do_notify_parent_cldstop(current, false, why);
 
-		/*
-		 * Don't want to allow preemption here, because
-		 * sys_ptrace() needs this task to be inactive.
-		 *
-		 * XXX: implement read_unlock_no_resched().
-		 */
-		preempt_disable();
 		read_unlock(&tasklist_lock);
-		preempt_enable_no_resched();
 		freezable_schedule();
 	} else {
 		/*