From patchwork Wed Aug 14 20:20:24 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Daniel Vetter X-Patchwork-Id: 11094465 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 98F851399 for ; Wed, 14 Aug 2019 20:20:47 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 870AA28800 for ; Wed, 14 Aug 2019 20:20:47 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 7AE0928837; Wed, 14 Aug 2019 20:20:47 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id CBE9A28800 for ; Wed, 14 Aug 2019 20:20:46 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 556096E831; Wed, 14 Aug 2019 20:20:40 +0000 (UTC) X-Original-To: dri-devel@lists.freedesktop.org Delivered-To: dri-devel@lists.freedesktop.org Received: from mail-ed1-x542.google.com (mail-ed1-x542.google.com [IPv6:2a00:1450:4864:20::542]) by gabe.freedesktop.org (Postfix) with ESMTPS id 1749E6E82D for ; Wed, 14 Aug 2019 20:20:38 +0000 (UTC) Received: by mail-ed1-x542.google.com with SMTP id a21so334209edt.11 for ; Wed, 14 Aug 2019 13:20:37 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=JoaO8Qe6CY1dfta4yCfl+sTgCnZHzLR+xJsBydvmafY=; b=IxwMYyuDf3MNTl3r7c7phLxWqo/NVkj175xSWkSGm4hDmz2lqZTgpvuSakDtsDKB+O o/Jt/3UfxCj70vxR6a634pClvWCQfmn2q0dTIVUuWxy7+IMGkdSzSc6LuYuG0UJdjaej fDtO5klCtHtLqRO9zl5AC2XAz7gm4nT7KyNMbwf8PvTwM2W9sz9nRtvjnOMV6j1SEBGO WL0dZhX+7l5SxX6tK7qhaeZS+go0/wjxehPgRQlp12OUeIUzHyfTBRjC9RcrK+lyGA+/ Mlr8bOSrYDXcKJvnM/6WJmQ7X//+J371pdoQBVTUEHaYRRPsajSNFtO+qjWrwf8eISJ6 OVXA== X-Gm-Message-State: APjAAAWO/U38QM/A9tZzmHwSygyGOh+b1E3DmDTQmFq/chfVR3TGpGPa RgmeRUu/nyGIlZdwotqofkW9Uw== X-Google-Smtp-Source: APXvYqwfgJdqGV4TaVUUi1ZAyfmEy0estN74mYOzE8kf3NhnJNKCPuqJA+FY/2vvG54TdUF778ZM6A== X-Received: by 2002:a17:906:198e:: with SMTP id g14mr1315533ejd.158.1565814036543; Wed, 14 Aug 2019 13:20:36 -0700 (PDT) Received: from phenom.ffwll.local ([2a02:168:569e:0:3106:d637:d723:e855]) by smtp.gmail.com with ESMTPSA id ns22sm84342ejb.9.2019.08.14.13.20.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 14 Aug 2019 13:20:35 -0700 (PDT) From: Daniel Vetter To: LKML Subject: [PATCH 2/5] kernel.h: Add non_block_start/end() Date: Wed, 14 Aug 2019 22:20:24 +0200 Message-Id: <20190814202027.18735-3-daniel.vetter@ffwll.ch> X-Mailer: git-send-email 2.22.0 In-Reply-To: <20190814202027.18735-1-daniel.vetter@ffwll.ch> References: <20190814202027.18735-1-daniel.vetter@ffwll.ch> MIME-Version: 1.0 X-Mailman-Original-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=JoaO8Qe6CY1dfta4yCfl+sTgCnZHzLR+xJsBydvmafY=; b=TB/fDwiRpXDbYnbebe5pI330088X9XJlGQF+2IhRTfDYTMEq0INaebPwZsNsT8LD80 +k2xt/FCnylJAZNGoH8zeEPnqj8+2txInoicG9vpjAfteV/ICjiT5gaNMKKQtYsYkrzg KNkRLGmFFbDP5EJsNKo7E/q8ZnanOmEVhmVQY= X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Feng Tang , Michal Hocko , Kees Cook , linux-mm@kvack.org, Peter Zijlstra , Daniel Vetter , Intel Graphics Development , Jann Horn , DRI Development , Jason Gunthorpe , =?utf-8?b?SsOpcsO0bWUgR2xpc3Nl?= , Ingo Molnar , Thomas Gleixner , Randy Dunlap , David Rientjes , Wei Wang , Daniel Vetter , Andrew Morton , Andy Shevchenko , =?utf-8?q?Christian_K?= =?utf-8?q?=C3=B6nig?= , Masahiro Yamada Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" X-Virus-Scanned: ClamAV using ClamSMTP In some special cases we must not block, but there's not a spinlock, preempt-off, irqs-off or similar critical section already that arms the might_sleep() debug checks. Add a non_block_start/end() pair to annotate these. This will be used in the oom paths of mmu-notifiers, where blocking is not allowed to make sure there's forward progress. Quoting Michal: "The notifier is called from quite a restricted context - oom_reaper - which shouldn't depend on any locks or sleepable conditionals. The code should be swift as well but we mostly do care about it to make a forward progress. Checking for sleepable context is the best thing we could come up with that would describe these demands at least partially." Peter also asked whether we want to catch spinlocks on top, but Michal said those are less of a problem because spinlocks can't have an indirect dependency upon the page allocator and hence close the loop with the oom reaper. Suggested by Michal Hocko. v2: - Improve commit message (Michal) - Also check in schedule, not just might_sleep (Peter) v3: It works better when I actually squash in the fixup I had lying around :-/ Cc: Jason Gunthorpe Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Andrew Morton Cc: Michal Hocko Cc: David Rientjes Cc: "Christian König" Cc: Daniel Vetter Cc: "Jérôme Glisse" Cc: linux-mm@kvack.org Cc: Masahiro Yamada Cc: Wei Wang Cc: Andy Shevchenko Cc: Thomas Gleixner Cc: Jann Horn Cc: Feng Tang Cc: Kees Cook Cc: Randy Dunlap Cc: linux-kernel@vger.kernel.org Acked-by: Christian König (v1) Signed-off-by: Daniel Vetter --- include/linux/kernel.h | 10 +++++++++- include/linux/sched.h | 4 ++++ kernel/sched/core.c | 19 ++++++++++++++----- 3 files changed, 27 insertions(+), 6 deletions(-) diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 4fa360a13c1e..915fd9888afb 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -217,7 +217,9 @@ extern void __cant_sleep(const char *file, int line, int preempt_offset); * might_sleep - annotation for functions that can sleep * * this macro will print a stack trace if it is executed in an atomic - * context (spinlock, irq-handler, ...). + * context (spinlock, irq-handler, ...). Additional sections where blocking is + * not allowed can be annotated with non_block_start() and non_block_end() + * pairs. * * This is a useful debugging help to be able to catch problems early and not * be bitten later when the calling function happens to sleep when it is not @@ -233,6 +235,10 @@ extern void __cant_sleep(const char *file, int line, int preempt_offset); # define cant_sleep() \ do { __cant_sleep(__FILE__, __LINE__, 0); } while (0) # define sched_annotate_sleep() (current->task_state_change = 0) +# define non_block_start() \ + do { current->non_block_count++; } while (0) +# define non_block_end() \ + do { WARN_ON(current->non_block_count-- == 0); } while (0) #else static inline void ___might_sleep(const char *file, int line, int preempt_offset) { } @@ -241,6 +247,8 @@ extern void __cant_sleep(const char *file, int line, int preempt_offset); # define might_sleep() do { might_resched(); } while (0) # define cant_sleep() do { } while (0) # define sched_annotate_sleep() do { } while (0) +# define non_block_start() do { } while (0) +# define non_block_end() do { } while (0) #endif #define might_sleep_if(cond) do { if (cond) might_sleep(); } while (0) diff --git a/include/linux/sched.h b/include/linux/sched.h index 9f51932bd543..c5630f3dca1f 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -974,6 +974,10 @@ struct task_struct { struct mutex_waiter *blocked_on; #endif +#ifdef CONFIG_DEBUG_ATOMIC_SLEEP + int non_block_count; +#endif + #ifdef CONFIG_TRACE_IRQFLAGS unsigned int irq_events; unsigned long hardirq_enable_ip; diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 2b037f195473..57245770d6cc 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3700,13 +3700,22 @@ static noinline void __schedule_bug(struct task_struct *prev) /* * Various schedule()-time debugging checks and statistics: */ -static inline void schedule_debug(struct task_struct *prev) +static inline void schedule_debug(struct task_struct *prev, bool preempt) { #ifdef CONFIG_SCHED_STACK_END_CHECK if (task_stack_end_corrupted(prev)) panic("corrupted stack end detected inside scheduler\n"); #endif +#ifdef CONFIG_DEBUG_ATOMIC_SLEEP + if (!preempt && prev->state && prev->non_block_count) { + printk(KERN_ERR "BUG: scheduling in a non-blocking section: %s/%d/%i\n", + prev->comm, prev->pid, prev->non_block_count); + dump_stack(); + add_taint(TAINT_WARN, LOCKDEP_STILL_OK); + } +#endif + if (unlikely(in_atomic_preempt_off())) { __schedule_bug(prev); preempt_count_set(PREEMPT_DISABLED); @@ -3813,7 +3822,7 @@ static void __sched notrace __schedule(bool preempt) rq = cpu_rq(cpu); prev = rq->curr; - schedule_debug(prev); + schedule_debug(prev, preempt); if (sched_feat(HRTICK)) hrtick_clear(rq); @@ -6570,7 +6579,7 @@ void ___might_sleep(const char *file, int line, int preempt_offset) rcu_sleep_check(); if ((preempt_count_equals(preempt_offset) && !irqs_disabled() && - !is_idle_task(current)) || + !is_idle_task(current) && !current->non_block_count) || system_state == SYSTEM_BOOTING || system_state > SYSTEM_RUNNING || oops_in_progress) return; @@ -6586,8 +6595,8 @@ void ___might_sleep(const char *file, int line, int preempt_offset) "BUG: sleeping function called from invalid context at %s:%d\n", file, line); printk(KERN_ERR - "in_atomic(): %d, irqs_disabled(): %d, pid: %d, name: %s\n", - in_atomic(), irqs_disabled(), + "in_atomic(): %d, irqs_disabled(): %d, non_block: %d, pid: %d, name: %s\n", + in_atomic(), irqs_disabled(), current->non_block_count, current->pid, current->comm); if (task_stack_end_corrupted(current))