LKML Archive on lore.kernel.org
 help / color / Atom feed
From: Thomas Gleixner <tglx@linutronix.de>
To: LKML <linux-kernel@vger.kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@kernel.org>, Darren Hart <darren@dvhart.com>,
	Yi Wang <wang.yi59@zte.com.cn>, Yang Tao <yang.tao172@zte.com.cn>,
	Oleg Nesterov <oleg@redhat.com>,
	Florian Weimer <fweimer@redhat.com>,
	Carlos O'Donell <carlos@redhat.com>,
	Alexander Viro <viro@zeniv.linux.org.uk>
Subject: [patch 08/12] futex: Sanitize exit state handling
Date: Wed, 06 Nov 2019 22:55:42 +0100
Message-ID: <20191106224556.645603214@linutronix.de> (raw)
In-Reply-To: <20191106215534.241796846@linutronix.de>

Instead of having a smp_mb() and an empty lock/unlock of task::pi_lock move
the state setting into to the lock section.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 kernel/futex.c |   17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -3703,16 +3703,19 @@ void futex_exit_done(struct task_struct
 
 void futex_exit_release(struct task_struct *tsk)
 {
-	tsk->futex_state = FUTEX_STATE_EXITING;
-	/*
-	 * Ensure that all new tsk->pi_lock acquisitions must observe
-	 * FUTEX_STATE_EXITING. Serializes against attach_to_pi_owner().
-	 */
-	smp_mb();
 	/*
-	 * Ensure that we must observe the pi_state in exit_pi_state_list().
+	 * Switch the state to FUTEX_STATE_EXITING under tsk->pi_lock.
+	 *
+	 * This ensures that all subsequent checks of tsk->futex_state in
+	 * attach_to_pi_owner() must observe FUTEX_STATE_EXITING with
+	 * tsk->pi_lock held.
+	 *
+	 * It guarantees also that a pi_state which was queued right before
+	 * the state change under tsk->pi_lock by a concurrent waiter must
+	 * be observed in exit_pi_state_list().
 	 */
 	raw_spin_lock_irq(&tsk->pi_lock);
+	tsk->futex_state = FUTEX_STATE_EXITING;
 	raw_spin_unlock_irq(&tsk->pi_lock);
 
 	futex_exec_release(tsk);



  parent reply index

Thread overview: 53+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-06 21:55 [patch 00/12] futex: Cure robust/PI futex exit races Thomas Gleixner
2019-11-06 21:55 ` [patch 01/12] futex: Prevent robust futex exit race Thomas Gleixner
2019-11-06 21:55 ` [patch 02/12] futex: Move futex exit handling into futex code Thomas Gleixner
2019-11-07  9:24   ` Peter Zijlstra
2019-11-07  9:38     ` Thomas Gleixner
2019-11-15 18:19   ` [tip: locking/core] " tip-bot2 for Thomas Gleixner
2019-11-16 20:53     ` Borislav Petkov
2019-11-20  9:38   ` tip-bot2 for Thomas Gleixner
2019-11-06 21:55 ` [patch 03/12] futex: Replace PF_EXITPIDONE with a state Thomas Gleixner
2019-11-15 18:19   ` [tip: locking/core] " tip-bot2 for Thomas Gleixner
2019-11-20  9:38   ` tip-bot2 for Thomas Gleixner
2019-11-06 21:55 ` [patch 04/12] exit/exec: Seperate mm_release() Thomas Gleixner
2019-11-15 18:19   ` [tip: locking/core] " tip-bot2 for Thomas Gleixner
2019-11-20  9:38   ` tip-bot2 for Thomas Gleixner
2019-11-06 21:55 ` [patch 05/12] futex: Split futex_mm_release() for exit/exec Thomas Gleixner
2019-11-15 18:19   ` [tip: locking/core] " tip-bot2 for Thomas Gleixner
2019-11-20  9:38   ` tip-bot2 for Thomas Gleixner
2019-11-06 21:55 ` [patch 06/12] futex: Set task::futex state to DEAD right after handling futex exit Thomas Gleixner
2019-11-15 18:19   ` [tip: locking/core] futex: Set task::futex_state " tip-bot2 for Thomas Gleixner
2019-11-20  9:38   ` tip-bot2 for Thomas Gleixner
2019-11-06 21:55 ` [patch 07/12] futex: Mark the begin of futex exit explicitly Thomas Gleixner
2019-11-15 18:19   ` [tip: locking/core] " tip-bot2 for Thomas Gleixner
2019-11-20  9:38   ` tip-bot2 for Thomas Gleixner
2019-11-06 21:55 ` Thomas Gleixner [this message]
2019-11-07  9:38   ` [patch 08/12] futex: Sanitize exit state handling Peter Zijlstra
2019-11-15 18:19   ` [tip: locking/core] " tip-bot2 for Thomas Gleixner
2019-11-20  9:38   ` tip-bot2 for Thomas Gleixner
2019-11-06 21:55 ` [patch 09/12] futex: Provide state handling for exec() as well Thomas Gleixner
2019-11-07  9:49   ` Peter Zijlstra
2019-11-07  9:54     ` Thomas Gleixner
2019-11-15 18:19   ` [tip: locking/core] " tip-bot2 for Thomas Gleixner
2019-11-20  9:38   ` tip-bot2 for Thomas Gleixner
2019-11-06 21:55 ` [patch 10/12] futex: Add mutex around futex exit Thomas Gleixner
2019-11-15 18:19   ` [tip: locking/core] " tip-bot2 for Thomas Gleixner
2019-11-20  9:38   ` tip-bot2 for Thomas Gleixner
2019-11-06 21:55 ` [patch 11/12] futex: Provide distinct return value when owner is exiting Thomas Gleixner
2019-11-15 18:19   ` [tip: locking/core] " tip-bot2 for Thomas Gleixner
2019-11-20  9:38   ` tip-bot2 for Thomas Gleixner
2019-11-06 21:55 ` [patch 12/12] futex: Prevent exit livelock Thomas Gleixner
2019-11-15 18:19   ` [tip: locking/core] " tip-bot2 for Thomas Gleixner
2019-11-20  9:38   ` tip-bot2 for Thomas Gleixner
2019-11-07  8:29 ` [patch 00/12] futex: Cure robust/PI futex exit races Ingo Molnar
2019-11-07  8:41 ` Ingo Molnar
2019-11-07  9:40 ` Peter Zijlstra
2019-11-07 15:03 ` Oleg Nesterov
2019-11-07 22:29 ` Florian Weimer
2019-11-07 22:40   ` Florian Weimer
2019-11-08  7:38     ` Florian Weimer
2019-11-08  9:18       ` Thomas Gleixner
2019-11-08 10:17         ` Florian Weimer
2019-11-08 10:37           ` Thomas Gleixner
2019-11-08 11:51             ` Thomas Gleixner
2019-11-11  9:48               ` Florian Weimer

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20191106224556.645603214@linutronix.de \
    --to=tglx@linutronix.de \
    --cc=carlos@redhat.com \
    --cc=darren@dvhart.com \
    --cc=fweimer@redhat.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@kernel.org \
    --cc=oleg@redhat.com \
    --cc=peterz@infradead.org \
    --cc=viro@zeniv.linux.org.uk \
    --cc=wang.yi59@zte.com.cn \
    --cc=yang.tao172@zte.com.cn \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

LKML Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/lkml/0 lkml/git/0.git
	git clone --mirror https://lore.kernel.org/lkml/1 lkml/git/1.git
	git clone --mirror https://lore.kernel.org/lkml/2 lkml/git/2.git
	git clone --mirror https://lore.kernel.org/lkml/3 lkml/git/3.git
	git clone --mirror https://lore.kernel.org/lkml/4 lkml/git/4.git
	git clone --mirror https://lore.kernel.org/lkml/5 lkml/git/5.git
	git clone --mirror https://lore.kernel.org/lkml/6 lkml/git/6.git
	git clone --mirror https://lore.kernel.org/lkml/7 lkml/git/7.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 lkml lkml/ https://lore.kernel.org/lkml \
		linux-kernel@vger.kernel.org
	public-inbox-index lkml

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-kernel


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git