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=-8.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham 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 9239CC04AAF for ; Tue, 21 May 2019 14:49:00 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 3C7CE21743 for ; Tue, 21 May 2019 14:49:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=ffwll.ch header.i=@ffwll.ch header.b="K2u0HR8G" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3C7CE21743 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ffwll.ch Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id D93266B000A; Tue, 21 May 2019 10:48:59 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D42DB6B000D; Tue, 21 May 2019 10:48:59 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C0AEB6B000E; Tue, 21 May 2019 10:48:59 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from mail-ed1-f71.google.com (mail-ed1-f71.google.com [209.85.208.71]) by kanga.kvack.org (Postfix) with ESMTP id 6F0786B000A for ; Tue, 21 May 2019 10:48:59 -0400 (EDT) Received: by mail-ed1-f71.google.com with SMTP id h12so30957669edl.23 for ; Tue, 21 May 2019 07:48:59 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:dkim-signature:sender:date:from:to:cc:subject :message-id:mail-followup-to:references:mime-version :content-disposition:content-transfer-encoding:in-reply-to :user-agent; bh=7IOMcNShzp88plVKB970+NE4F+uWKbqTavdIwV9VTZU=; b=HVfldeCa4WOd16pwQZ66AHbVHg4T5EiJvOPcogzApiIOBJmGs94xQDMmlUYEjd8o1d BN5yvfP/+tI2hpVKJcXNvUQe+btrPl78y9u6o1vzCJuq0vbe+BkLYUqN6cn46bBB43aW hTFIbfTgplfadMnRx2SKEOsodiV4zI9o3bQpUXVQOgouEwy3L/H4jNyfLoGvwjiwOrTy YlZnpwg13YtvfrLk7vQ3lqboK4sTOTPgQjxh/aXg5OkYPhPv9fROV4ulk7UOOmufNzC/ 4zvggTdLLsv7wzSSt+o93jAE24uRxsiKGaJSfzpXm71jPX5SDPPQKtC2c7pYJnnbpz0C FaxQ== X-Gm-Message-State: APjAAAXSMF5pL2YX1Jw8oCVyq1ODWb6ETBA0wyQdLZgobOtrRCoVAJ4A HgxYAhAtN3PMjqTh1yqUxOEAmgZgYE+ocnTtSlcwEqYDnkfAJSxVEg1vjz8utKThGfWurYXupJP faBfes4lxW7VfpQVsz9UjoBp4OLB5bRm88PV99eqPxA/0Pt0VB3o26Ubc30r8556PzQ== X-Received: by 2002:a17:906:f84a:: with SMTP id ks10mr47679422ejb.65.1558450138964; Tue, 21 May 2019 07:48:58 -0700 (PDT) X-Received: by 2002:a17:906:f84a:: with SMTP id ks10mr47679345ejb.65.1558450137998; Tue, 21 May 2019 07:48:57 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1558450137; cv=none; d=google.com; s=arc-20160816; b=xoV7oWJLzg+V+YONFjtj8jx0ZAkH7SUil3rRooJ9bHhKHQSJSDjdvBu5HjrkneG39D XxZgrx6W0XrW3xgFZaEBw5yyaxdWBPvB8m7OcaiHvE62ybWAonzS4og7NFcC/u/3OP9n Sr8A1mea0FzIXmzGo9yLBP81YRz911Q6rZkUpc3XacZqSsE1YXmgbPWZ3nI93jFqEeGr mzYEa3rMUjtX4+KGaunYgil0Dh/AQGztKtw3zI5iODVW7VxICATS26J/wQTPkICAwJCb vAoo/XVJwUf7SAjVNPgLS89o5jpwbd64kSf6SqzzLeWvwP/HlEazBZWwV+A20FwRQltn O2Gw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=user-agent:in-reply-to:content-transfer-encoding :content-disposition:mime-version:references:mail-followup-to :message-id:subject:cc:to:from:date:sender:dkim-signature; bh=7IOMcNShzp88plVKB970+NE4F+uWKbqTavdIwV9VTZU=; b=ly7DjuMdfXhZulkQSvWgj1mdKQ8gFtfhtbHQ5bQnlAPRPxNw+6h+m7JS/gj6+IDh1Y sml68HhKfq9XNQSh0+o95rMD4WPv8rGqMsg4UP3YAsfefi+PKxcCodVhKAa3L4ulGUcG jsv5VIi0DSr5itkV3oaFvcFhnRLgNt8AJC3/dL/oZr0GZX5wUi4nwh9tm2Az1o1R5WPL rnIJz3BhBkex3busAVzyeUBuSOgnFigvAZz/mwmCcuTrQcCbpvjQaUSPzh39W8ncWVKk twoXMSAEvXTppOQSf20THCohHi4O80haeg2oxKgdbnBe7EdQb4z4R541NwRtl852zxTz 3HFQ== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@ffwll.ch header.s=google header.b=K2u0HR8G; spf=neutral (google.com: 209.85.220.65 is neither permitted nor denied by best guess record for domain of daniel@ffwll.ch) smtp.mailfrom=daniel@ffwll.ch Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id 33sor2138409eds.23.2019.05.21.07.48.57 for (Google Transport Security); Tue, 21 May 2019 07:48:57 -0700 (PDT) Received-SPF: neutral (google.com: 209.85.220.65 is neither permitted nor denied by best guess record for domain of daniel@ffwll.ch) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@ffwll.ch header.s=google header.b=K2u0HR8G; spf=neutral (google.com: 209.85.220.65 is neither permitted nor denied by best guess record for domain of daniel@ffwll.ch) smtp.mailfrom=daniel@ffwll.ch DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=sender:date:from:to:cc:subject:message-id:mail-followup-to :references:mime-version:content-disposition :content-transfer-encoding:in-reply-to:user-agent; bh=7IOMcNShzp88plVKB970+NE4F+uWKbqTavdIwV9VTZU=; b=K2u0HR8GjjPph9aWDUMgbUTkdaGHORgnlhQ5O+jE9OPB0bYVQnJ1ODz4blADryQtdX pa0G0gEFYE0rz9UvMpOgqbe+rbO0ivH/HD50iXsv/+brZ/19ysThpf/RfyS0dqkSUiG2 Of+EbAXOcS1PLLjYqc3MNnAPJwN2wV4XxglRA= X-Google-Smtp-Source: APXvYqytIZu/6anacKvD69vhQKlzZMTSzIMEvW9ZHTiye+AtpdGee4CjEbWTItKCYEIqDaw+ejs+4Q== X-Received: by 2002:a50:8808:: with SMTP id b8mr54195428edb.202.1558450137617; Tue, 21 May 2019 07:48:57 -0700 (PDT) Received: from phenom.ffwll.local ([2a02:168:569e:0:3106:d637:d723:e855]) by smtp.gmail.com with ESMTPSA id t19sm3558423ejq.51.2019.05.21.07.48.56 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 21 May 2019 07:48:56 -0700 (PDT) Date: Tue, 21 May 2019 16:48:54 +0200 From: Daniel Vetter To: Michal Hocko Cc: Daniel Vetter , DRI Development , Intel Graphics Development , LKML , Linux MM , Peter Zijlstra , Ingo Molnar , Andrew Morton , David Rientjes , Christian =?iso-8859-1?Q?K=F6nig?= , =?iso-8859-1?B?Suly9G1l?= Glisse , Masahiro Yamada , Wei Wang , Andy Shevchenko , Thomas Gleixner , Jann Horn , Feng Tang , Kees Cook , Randy Dunlap , Daniel Vetter Subject: Re: [PATCH] kernel.h: Add non_block_start/end() Message-ID: <20190521144854.GP21222@phenom.ffwll.local> Mail-Followup-To: Michal Hocko , DRI Development , Intel Graphics Development , LKML , Linux MM , Peter Zijlstra , Ingo Molnar , Andrew Morton , David Rientjes , Christian =?iso-8859-1?Q?K=F6nig?= , =?iso-8859-1?B?Suly9G1l?= Glisse , Masahiro Yamada , Wei Wang , Andy Shevchenko , Thomas Gleixner , Jann Horn , Feng Tang , Kees Cook , Randy Dunlap , Daniel Vetter References: <20190521100611.10089-1-daniel.vetter@ffwll.ch> <20190521104638.GO32329@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20190521104638.GO32329@dhcp22.suse.cz> X-Operating-System: Linux phenom 4.14.0-3-amd64 User-Agent: Mutt/1.10.1 (2018-07-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, May 21, 2019 at 12:46:38PM +0200, Michal Hocko wrote: > On Tue 21-05-19 12:06:11, Daniel Vetter wrote: > > 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: 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 > > I like this in general. The implementation looks reasonable to me but I > didn't check deeply enough to give my R-by or A-by. Thanks for all your comments. I'll ask Jerome Glisse to look into this, I think it'd could be useful for all the HMM work too. And I sent this out without reply-to the patch it's supposed to replace, will need to do that again so patchwork and 0day pick up the correct series. Sry about that noise :-/ -Daniel > > > --- > > 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 74b1ee9027f5..b5f2c2ff0eab 100644 > > --- a/include/linux/kernel.h > > +++ b/include/linux/kernel.h > > @@ -214,7 +214,9 @@ 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 > > @@ -230,6 +232,10 @@ 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) { } > > @@ -238,6 +244,8 @@ 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 11837410690f..7f5b293e72df 100644 > > --- a/include/linux/sched.h > > +++ b/include/linux/sched.h > > @@ -908,6 +908,10 @@ 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 102dfcf0a29a..ed7755a28465 100644 > > --- a/kernel/sched/core.c > > +++ b/kernel/sched/core.c > > @@ -3264,13 +3264,22 @@ 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); > > @@ -3377,7 +3386,7 @@ 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); > > @@ -6102,7 +6111,7 @@ 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; > > @@ -6118,8 +6127,8 @@ 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)) > > -- > > 2.20.1 > > > > -- > Michal Hocko > SUSE Labs -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch