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bh=X1Gjbn7bSatPmLMP7OcwtXOBlb5rE9gVl2DfyPsZLUU=; b=B2OLAuG6VG1KlURRaOQwrhrXRIqNfawyjYGQC1kw4242Z477wws9vI2sxTvLZFZylkWoAF cASIQp9m65nlLMjXkLyyafLvDf+EJFSaL/IuFRNQNGFC5gwdD7CK5TOYu5Gi074jcsCBc4 GWpHOmb9Z3i3NpxAGZNKHY17iwYCFrzv60YgW0nNa0ukR4epz0MZR8XmdjawL3f+I7f4vM LTwRowOtXuT07PYxyvbM0Rcb3I5yEPoabRg2vrJbQG8jvTydXwjyS8MwefILBfBHc1Oz1R zRe5TXrSS6JOA89bSBLxXW966V8BDLsJ8jrkBnW05H52XLzRomOe63/uac3aQg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1732289348; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=X1Gjbn7bSatPmLMP7OcwtXOBlb5rE9gVl2DfyPsZLUU=; b=ZNbS6YZKwcTBvmOMUMJyOIS8J3Qs40yGMmEC+bJoPHH1KiSaWbmtaYw696eaaIi930pJan WEbQiUPwLD7YuTDA== From: Sebastian Andrzej Siewior To: Marco Elver Cc: Andrey Konovalov , Peter Zijlstra , Vlastimil Babka , syzbot , Liam.Howlett@oracle.com, akpm@linux-foundation.org, jannh@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lorenzo.stoakes@oracle.com, syzkaller-bugs@googlegroups.com, kasan-dev , Andrey Ryabinin , Alexander Potapenko , Waiman Long , dvyukov@google.com, vincenzo.frascino@arm.com, paulmck@kernel.org, frederic@kernel.org, neeraj.upadhyay@kernel.org, joel@joelfernandes.org, josh@joshtriplett.org, boqun.feng@gmail.com, urezki@gmail.com, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, qiang.zhang1211@gmail.com, mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, tj@kernel.org, cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, Thomas Gleixner , roman.gushchin@linux.dev, 42.hyeyoo@gmail.com, rcu@vger.kernel.org Subject: Re: [PATCH] kasan: Remove kasan_record_aux_stack_noalloc(). Message-ID: <20241122152905.iyjG97GS@linutronix.de> References: <67275485.050a0220.3c8d68.0a37.GAE@google.com> <20241104114506.GC24862@noisy.programming.kicks-ass.net> <20241119155701.GYennzPF@linutronix.de> <20241122113210.QxE7YOwK@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 4C67A1C0011 X-Stat-Signature: wuadowx5ub57gnzgx4mnmsycu8kra985 X-Rspam-User: X-HE-Tag: 1732289326-695705 X-HE-Meta: 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 fcD8Tdr4 fifx8gnDEDqq6EngMcig0OxqaOmZENbbZtorSW3DbzyKzP0/T5CzJH2qNZJopxcq6x+FjbrnXvqCtA3MHglh4ID4kjvjui5MgG3wpBc6AMg4tC5eGFoX3/ZQ6apK+oewW9sc7fJutuzJ3DoYVPu6QZ+YXNVZ5H142BK2QS4T2+RY044FpAe+uldnfTUqqZ7o+7WHTRdybwVu3jMZ93haDb1mVCXlRgAczjPzvasSzYFW5nPmB90XuOoPP9BpbGHsVhKNTlnNAXTxz4bQezEI0N+z73YJG3qs2zrHC8N0sz268P8gKLx1tH6gaYg== 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: List-Subscribe: List-Unsubscribe: On 2024-11-22 16:01:29 [+0100], Marco Elver wrote: > > Do we need to update the comment saying that it must not be used from > > NMI or do we make it jump over the locked section in the NMI case? > > Good point. It was meant to also be usable from NMI, because it's very > likely to succeed, and should just take the lock-less fast path once the > stack is in the depot. > > But I think we need a fix like this for initial saving of a stack trace: > > > diff --git a/lib/stackdepot.c b/lib/stackdepot.c > index 5ed34cc963fc..245d5b416699 100644 > --- a/lib/stackdepot.c > +++ b/lib/stackdepot.c > @@ -630,7 +630,15 @@ depot_stack_handle_t stack_depot_save_flags(unsigned long *entries, > prealloc = page_address(page); > } > > - raw_spin_lock_irqsave(&pool_lock, flags); > + if (in_nmi()) { > + /* We can never allocate in NMI context. */ > + WARN_ON_ONCE(can_alloc); > + /* Best effort; bail if we fail to take the lock. */ > + if (!raw_spin_trylock_irqsave(&pool_lock, flags)) > + goto exit; > + } else { > + raw_spin_lock_irqsave(&pool_lock, flags); > + } > printk_deferred_enter(); > > /* Try to find again, to avoid concurrently inserting duplicates. */ > > > If that looks reasonable, I'll turn it into a patch. Yes, looks reasonable. Sebastian