From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EB268C3A59E for ; Wed, 21 Aug 2019 19:31:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B2B1F20679 for ; Wed, 21 Aug 2019 19:31:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730427AbfHUTbi (ORCPT ); Wed, 21 Aug 2019 15:31:38 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:57373 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730275AbfHUTbQ (ORCPT ); Wed, 21 Aug 2019 15:31:16 -0400 Received: from localhost ([127.0.0.1] helo=nanos.tec.linutronix.de) by Galois.linutronix.de with esmtp (Exim 4.80) (envelope-from ) id 1i0WK8-0004HS-0o; Wed, 21 Aug 2019 21:31:12 +0200 Message-Id: <20190821192922.743229404@linutronix.de> User-Agent: quilt/0.65 Date: Wed, 21 Aug 2019 21:09:24 +0200 From: Thomas Gleixner To: LKML Cc: Oleg Nesterov , Ingo Molnar , Peter Zijlstra , John Stultz , Frederic Weisbecker , Anna-Maria Behnsen , Christoph Hellwig Subject: [patch V2 37/38] posix-cpu-timers: Move state tracking to struct posix_cputimers References: <20190821190847.665673890@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Put it where it belongs and clean up the ifdeffery in fork completely. Signed-off-by: Thomas Gleixner --- V2: Adopt to the per clock base struct --- include/linux/posix-timers.h | 8 ++++ include/linux/sched/cputime.h | 9 +++-- include/linux/sched/signal.h | 6 --- init/init_task.c | 2 - kernel/fork.c | 6 --- kernel/time/posix-cpu-timers.c | 73 ++++++++++++++++++++++------------------- 6 files changed, 54 insertions(+), 50 deletions(-) --- a/include/linux/posix-timers.h +++ b/include/linux/posix-timers.h @@ -77,15 +77,23 @@ struct posix_cputimer_base { /** * posix_cputimers - Container for posix CPU timer related data * @bases: Base container for posix CPU clocks + * @timers_active: Timers are queued. + * @expiry_active: Timer expiry is active. Used for + * process wide timers to avoid multiple + * task trying to handle expiry concurrently * * Used in task_struct and signal_struct */ struct posix_cputimers { struct posix_cputimer_base bases[CPUCLOCK_MAX]; + unsigned int timers_active; + unsigned int expiry_active; }; static inline void posix_cputimers_init(struct posix_cputimers *pct) { + pct->timers_active = 0; + pct->expiry_active = 0; pct->bases[0].nextevt = U64_MAX; pct->bases[1].nextevt = U64_MAX; pct->bases[2].nextevt = U64_MAX; --- a/include/linux/sched/cputime.h +++ b/include/linux/sched/cputime.h @@ -70,7 +70,7 @@ void thread_group_sample_cputime(struct */ /** - * get_running_cputimer - return &tsk->signal->cputimer if cputimer is running + * get_running_cputimer - return &tsk->signal->cputimer if cputimers are active * * @tsk: Pointer to target task. */ @@ -80,8 +80,11 @@ struct thread_group_cputimer *get_runnin { struct thread_group_cputimer *cputimer = &tsk->signal->cputimer; - /* Check if cputimer isn't running. This is accessed without locking. */ - if (!READ_ONCE(cputimer->running)) + /* + * Check whether posix CPU timers are active. If not the thread + * group accounting is not active either. Lockless check. + */ + if (!READ_ONCE(tsk->signal->posix_cputimers.timers_active)) return NULL; /* --- a/include/linux/sched/signal.h +++ b/include/linux/sched/signal.h @@ -57,18 +57,12 @@ struct task_cputime_atomic { /** * struct thread_group_cputimer - thread group interval timer counts * @cputime_atomic: atomic thread group interval timers. - * @running: true when there are timers running and - * @cputime_atomic receives updates. - * @checking_timer: true when a thread in the group is in the - * process of checking for thread group timers. * * This structure contains the version of task_cputime, above, that is * used for thread group CPU timer calculations. */ struct thread_group_cputimer { struct task_cputime_atomic cputime_atomic; - bool running; - bool checking_timer; }; struct multiprocess_signals { --- a/init/init_task.c +++ b/init/init_task.c @@ -30,8 +30,6 @@ static struct signal_struct init_signals .posix_timers = LIST_HEAD_INIT(init_signals.posix_timers), .cputimer = { .cputime_atomic = INIT_CPUTIME_ATOMIC, - .running = false, - .checking_timer = false, }, #endif INIT_CPU_TIMERS(init_signals) --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1517,7 +1517,6 @@ void __cleanup_sighand(struct sighand_st } } -#ifdef CONFIG_POSIX_TIMERS /* * Initialize POSIX timer handling for a thread group. */ @@ -1528,12 +1527,7 @@ static void posix_cpu_timers_init_group( cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); posix_cputimers_group_init(pct, cpu_limit); - if (cpu_limit != RLIM_INFINITY) - sig->cputimer.running = true; } -#else -static inline void posix_cpu_timers_init_group(struct signal_struct *sig) { } -#endif static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) { --- a/kernel/time/posix-cpu-timers.c +++ b/kernel/time/posix-cpu-timers.c @@ -23,8 +23,10 @@ static void posix_cpu_timer_rearm(struct void posix_cputimers_group_init(struct posix_cputimers *pct, u64 cpu_limit) { posix_cputimers_init(pct); - if (cpu_limit != RLIM_INFINITY) + if (cpu_limit != RLIM_INFINITY) { pct->bases[CPUCLOCK_PROF].nextevt = cpu_limit * NSEC_PER_SEC; + pct->timers_active = true; + } } /* @@ -248,8 +250,9 @@ static void update_gt_cputime(struct tas void thread_group_sample_cputime(struct task_struct *tsk, u64 *samples) { struct thread_group_cputimer *cputimer = &tsk->signal->cputimer; + struct posix_cputimers *pct = &tsk->signal->posix_cputimers; - WARN_ON_ONCE(!cputimer->running); + WARN_ON_ONCE(!pct->timers_active); proc_sample_cputime_atomic(&cputimer->cputime_atomic, samples); } @@ -269,9 +272,10 @@ void thread_group_sample_cputime(struct static void thread_group_start_cputime(struct task_struct *tsk, u64 *samples) { struct thread_group_cputimer *cputimer = &tsk->signal->cputimer; + struct posix_cputimers *pct = &tsk->signal->posix_cputimers; /* Check if cputimer isn't running. This is accessed without locking. */ - if (!READ_ONCE(cputimer->running)) { + if (!READ_ONCE(pct->timers_active)) { struct task_cputime sum; /* @@ -283,13 +287,13 @@ static void thread_group_start_cputime(s update_gt_cputime(&cputimer->cputime_atomic, &sum); /* - * We're setting cputimer->running without a lock. Ensure - * this only gets written to in one operation. We set - * running after update_gt_cputime() as a small optimization, - * but barriers are not required because update_gt_cputime() + * We're setting timers_active without a lock. Ensure this + * only gets written to in one operation. We set it after + * update_gt_cputime() as a small optimization, but + * barriers are not required because update_gt_cputime() * can handle concurrent updates. */ - WRITE_ONCE(cputimer->running, true); + WRITE_ONCE(pct->timers_active, true); } proc_sample_cputime_atomic(&cputimer->cputime_atomic, samples); } @@ -313,9 +317,10 @@ static u64 cpu_clock_sample_group(const bool start) { struct thread_group_cputimer *cputimer = &p->signal->cputimer; + struct posix_cputimers *pct = &p->signal->posix_cputimers; u64 samples[CPUCLOCK_MAX]; - if (!READ_ONCE(cputimer->running)) { + if (!READ_ONCE(pct->timers_active)) { if (start) thread_group_start_cputime(p, samples); else @@ -834,10 +839,10 @@ static void check_thread_timers(struct t static inline void stop_process_timers(struct signal_struct *sig) { - struct thread_group_cputimer *cputimer = &sig->cputimer; + struct posix_cputimers *pct = &sig->posix_cputimers; - /* Turn off cputimer->running. This is done without locking. */ - WRITE_ONCE(cputimer->running, false); + /* Turn off the active flag. This is done without locking. */ + WRITE_ONCE(pct->timers_active, false); tick_dep_clear_signal(sig, TICK_DEP_BIT_POSIX_TIMER); } @@ -877,17 +882,17 @@ static void check_process_timers(struct unsigned long soft; /* - * If cputimer is not running, then there are no active - * process wide timers (POSIX 1.b, itimers, RLIMIT_CPU). + * If there are no active process wide timers (POSIX 1.b, itimers, + * RLIMIT_CPU) nothing to check. */ - if (!READ_ONCE(sig->cputimer.running)) + if (!READ_ONCE(pct->timers_active)) return; /* * Signify that a thread is checking for process timers. * Write access to this field is protected by the sighand lock. */ - sig->cputimer.checking_timer = true; + pct->timers_active = true; /* * Collect the current process totals. Group accounting is active @@ -933,7 +938,7 @@ static void check_process_timers(struct if (expiry_cache_is_inactive(pct)) stop_process_timers(sig); - sig->cputimer.checking_timer = false; + pct->expiry_active = false; } /* @@ -1027,39 +1032,41 @@ task_cputimers_expired(const u64 *sample */ static inline bool fastpath_timer_check(struct task_struct *tsk) { + struct posix_cputimers *pct = &tsk->posix_cputimers; struct signal_struct *sig; - if (!expiry_cache_is_inactive(&tsk->posix_cputimers)) { + if (!expiry_cache_is_inactive(pct)) { u64 samples[CPUCLOCK_MAX]; task_sample_cputime(tsk, samples); - if (task_cputimers_expired(samples, &tsk->posix_cputimers)) + if (task_cputimers_expired(samples, pct)) return true; } sig = tsk->signal; + pct = &sig->posix_cputimers; /* - * Check if thread group timers expired when the cputimer is - * running and no other thread in the group is already checking - * for thread group cputimers. These fields are read without the - * sighand lock. However, this is fine because this is meant to - * be a fastpath heuristic to determine whether we should try to - * acquire the sighand lock to check/handle timers. + * Check if thread group timers expired when timers are active and + * no other thread in the group is already handling expiry for + * thread group cputimers. These fields are read without the + * sighand lock. However, this is fine because this is meant to be + * a fastpath heuristic to determine whether we should try to + * acquire the sighand lock to handle timer expiry. * - * In the worst case scenario, if 'running' or 'checking_timer' gets - * set but the current thread doesn't see the change yet, we'll wait - * until the next thread in the group gets a scheduler interrupt to - * handle the timer. This isn't an issue in practice because these - * types of delays with signals actually getting sent are expected. + * In the worst case scenario, if concurrently timers_active is set + * or expiry_active is cleared, but the current thread doesn't see + * the change yet, the timer checks are delayed until the next + * thread in the group gets a scheduler interrupt to handle the + * timer. This isn't an issue in practice because these types of + * delays with signals actually getting sent are expected. */ - if (READ_ONCE(sig->cputimer.running) && - !READ_ONCE(sig->cputimer.checking_timer)) { + if (READ_ONCE(pct->timers_active) && !READ_ONCE(pct->expiry_active)) { u64 samples[CPUCLOCK_MAX]; proc_sample_cputime_atomic(&sig->cputimer.cputime_atomic, samples); - if (task_cputimers_expired(samples, &sig->posix_cputimers)) + if (task_cputimers_expired(samples, pct)) return true; }