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 10/12] futex: Add mutex around futex exit
Date: Wed, 06 Nov 2019 22:55:44 +0100 [thread overview]
Message-ID: <20191106224556.845798895@linutronix.de> (raw)
In-Reply-To: 20191106215534.241796846@linutronix.de
The mutex will be used in subsequent changes to replace the busy looping of
a waiter when the futex owner is currently executing the exit cleanup to
prevent a potential live lock.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
include/linux/futex.h | 1 +
include/linux/sched.h | 1 +
kernel/futex.c | 16 ++++++++++++++++
3 files changed, 18 insertions(+)
--- a/include/linux/futex.h
+++ b/include/linux/futex.h
@@ -63,6 +63,7 @@ static inline void futex_init_task(struc
INIT_LIST_HEAD(&tsk->pi_state_list);
tsk->pi_state_cache = NULL;
tsk->futex_state = FUTEX_STATE_OK;
+ mutex_init(&tsk->futex_exit_mutex);
}
void futex_exit_recursive(struct task_struct *tsk);
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1054,6 +1054,7 @@ struct task_struct {
#endif
struct list_head pi_state_list;
struct futex_pi_state *pi_state_cache;
+ struct mutex futex_exit_mutex;
unsigned int futex_state;
#endif
#ifdef CONFIG_PERF_EVENTS
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -3698,12 +3698,23 @@ static void futex_cleanup(struct task_st
*/
void futex_exit_recursive(struct task_struct *tsk)
{
+ /* If the state is FUTEX_STATE_EXITING then futex_exit_mutex is held */
+ if (tsk->futex_state == FUTEX_STATE_EXITING)
+ mutex_unlock(&tsk->futex_exit_mutex);
tsk->futex_state = FUTEX_STATE_DEAD;
}
static void futex_cleanup_begin(struct task_struct *tsk)
{
/*
+ * Prevent various race issues against a concurrent incoming waiter
+ * including live locks by forcing the waiter to block on
+ * tsk->futex_exit_mutex when it observes FUTEX_STATE_EXITING in
+ * attach_to_pi_owner().
+ */
+ mutex_lock(&tsk->futex_exit_mutex);
+
+ /*
* Switch the state to FUTEX_STATE_EXITING under tsk->pi_lock.
*
* This ensures that all subsequent checks of tsk->futex_state in
@@ -3726,6 +3737,11 @@ static void futex_cleanup_end(struct tas
* take another loop until it becomes visible.
*/
tsk->futex_state = state;
+ /*
+ * Drop the exit protection. This unblocks waiters which observed
+ * FUTEX_STATE_EXITING to reevaluate the state.
+ */
+ mutex_unlock(&tsk->futex_exit_mutex);
}
void futex_exec_release(struct task_struct *tsk)
next prev parent reply other threads:[~2019-11-06 23:08 UTC|newest]
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 ` [patch 08/12] futex: Sanitize exit state handling Thomas Gleixner
2019-11-07 9:38 ` 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 ` Thomas Gleixner [this message]
2019-11-15 18:19 ` [tip: locking/core] futex: Add mutex around futex exit 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 publicly 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=20191106224556.845798895@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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).