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[84.3.50.134]) by smtp.gmail.com with ESMTPSA id d5sm2737633eds.40.2020.07.25.03.47.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 25 Jul 2020 03:47:22 -0700 (PDT) Date: Sat, 25 Jul 2020 12:47:20 +0200 From: Ingo Molnar To: Linus Torvalds Cc: linux-kernel@vger.kernel.org, Peter Zijlstra , Thomas Gleixner Subject: [GIT PULL] scheduler fixes Message-ID: <20200725104720.GA824189@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Linus, Please pull the latest sched/urgent git tree from: git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git sched-urgent-2020-07-25 # HEAD: 062d3f95b630113e1156a31f376ad36e25da29a7 sched: Warn if garbage is passed to default_wake_function() Fix a race introduced by the recent loadavg race fix, plus add a debug check for a hard to debug case of bogus wakeup function flags. Thanks, Ingo ------------------> Chris Wilson (1): sched: Warn if garbage is passed to default_wake_function() Peter Zijlstra (1): sched: Fix race against ptrace_freeze_trace() kernel/sched/core.c | 25 +++++++++++++++---------- 1 file changed, 15 insertions(+), 10 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index e15543cb8481..2142c6767682 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4119,9 +4119,6 @@ static void __sched notrace __schedule(bool preempt) local_irq_disable(); rcu_note_context_switch(preempt); - /* See deactivate_task() below. */ - prev_state = prev->state; - /* * Make sure that signal_pending_state()->signal_pending() below * can't be reordered with __set_current_state(TASK_INTERRUPTIBLE) @@ -4145,11 +4142,16 @@ static void __sched notrace __schedule(bool preempt) update_rq_clock(rq); switch_count = &prev->nivcsw; + /* - * We must re-load prev->state in case ttwu_remote() changed it - * before we acquired rq->lock. + * We must load prev->state once (task_struct::state is volatile), such + * that: + * + * - we form a control dependency vs deactivate_task() below. + * - ptrace_{,un}freeze_traced() can change ->state underneath us. */ - if (!preempt && prev_state && prev_state == prev->state) { + prev_state = prev->state; + if (!preempt && prev_state) { if (signal_pending_state(prev_state, prev)) { prev->state = TASK_RUNNING; } else { @@ -4163,10 +4165,12 @@ static void __sched notrace __schedule(bool preempt) /* * __schedule() ttwu() - * prev_state = prev->state; if (READ_ONCE(p->on_rq) && ...) - * LOCK rq->lock goto out; - * smp_mb__after_spinlock(); smp_acquire__after_ctrl_dep(); - * p->on_rq = 0; p->state = TASK_WAKING; + * prev_state = prev->state; if (p->on_rq && ...) + * if (prev_state) goto out; + * p->on_rq = 0; smp_acquire__after_ctrl_dep(); + * p->state = TASK_WAKING + * + * Where __schedule() and ttwu() have matching control dependencies. * * After this, schedule() must not care about p->state any more. */ @@ -4481,6 +4485,7 @@ asmlinkage __visible void __sched preempt_schedule_irq(void) int default_wake_function(wait_queue_entry_t *curr, unsigned mode, int wake_flags, void *key) { + WARN_ON_ONCE(IS_ENABLED(CONFIG_SCHED_DEBUG) && wake_flags & ~WF_SYNC); return try_to_wake_up(curr->private, mode, wake_flags); } EXPORT_SYMBOL(default_wake_function);