From: "tip-bot2 for Thomas Gleixner" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
Borislav Petkov <bp@alien8.de>,
linux-kernel@vger.kernel.org
Subject: [tip: locking/core] futex: Add mutex around futex exit
Date: Fri, 15 Nov 2019 18:19:19 -0000 [thread overview]
Message-ID: <157384195951.12247.12809391379915950403.tip-bot2@tip-bot2> (raw)
In-Reply-To: <20191106224556.845798895@linutronix.de>
The following commit has been merged into the locking/core branch of tip:
Commit-ID: 599ab3f76ebd32a027b95429f47dea739a7458fd
Gitweb: https://git.kernel.org/tip/599ab3f76ebd32a027b95429f47dea739a7458fd
Author: Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Wed, 06 Nov 2019 22:55:44 +01:00
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Fri, 15 Nov 2019 19:10:53 +01:00
futex: Add mutex around futex exit
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>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20191106224556.845798895@linutronix.de
---
include/linux/futex.h | 1 +
include/linux/sched.h | 1 +
kernel/futex.c | 16 ++++++++++++++++
3 files changed, 18 insertions(+)
diff --git a/include/linux/futex.h b/include/linux/futex.h
index 9daf8d9..214284c 100644
--- a/include/linux/futex.h
+++ b/include/linux/futex.h
@@ -63,6 +63,7 @@ static inline void futex_init_task(struct task_struct *tsk)
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);
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 85dab2f..1ebe540 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1053,6 +1053,7 @@ 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
diff --git a/kernel/futex.c b/kernel/futex.c
index 0c9850a..46a81e6 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -3698,12 +3698,23 @@ static void futex_cleanup(struct task_struct *tsk)
*/
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 task_struct *tsk, int state)
* 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:[~2019-11-15 18:19 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 ` [patch 10/12] futex: Add mutex around futex exit Thomas Gleixner
2019-11-15 18:19 ` tip-bot2 for Thomas Gleixner [this message]
2019-11-20 9:38 ` [tip: locking/core] " 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
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