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McKenney" To: Vlastimil Babka Cc: Sebastian Andrzej Siewior , Marco Elver , linux-next@vger.kernel.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, sfr@canb.auug.org.au, longman@redhat.com, boqun.feng@gmail.com, cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org Subject: Re: [BUG] -next lockdep invalid wait context Message-ID: Reply-To: paulmck@kernel.org References: <41619255-cdc2-4573-a360-7794fc3614f7@paulmck-laptop> <66a745bb-d381-471c-aeee-3800a504f87d@paulmck-laptop> <20241031072136.JxDEfP5V@linutronix.de> <20241031075509.hCS9Amov@linutronix.de> <751e281a-126b-4bcd-8965-71affac4a783@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <751e281a-126b-4bcd-8965-71affac4a783@suse.cz> X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 222094000E X-Stat-Signature: 5dkkk5z3yenesx1brugmzof55r8uu6ix X-Rspam-User: X-HE-Tag: 1730481232-690283 X-HE-Meta: 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 A/LD1kA5 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 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 Thu, Oct 31, 2024 at 09:18:52AM +0100, Vlastimil Babka wrote: > On 10/31/24 08:55, Sebastian Andrzej Siewior wrote: > > On 2024-10-31 08:35:45 [+0100], Vlastimil Babka wrote: > >> On 10/31/24 08:21, Sebastian Andrzej Siewior wrote: > >> > On 2024-10-30 16:10:58 [-0700], Paul E. McKenney wrote: > >> >> > >> >> So I need to avoid calling kfree() within an smp_call_function() handler? > >> > > >> > Yes. No kmalloc()/ kfree() in IRQ context. > >> > >> However, isn't this the case that the rule is actually about hardirq context > >> on RT, and most of these operations that are in IRQ context on !RT become > >> the threaded interrupt context on RT, so they are actually fine? Or is smp > >> call callback a hardirq context on RT and thus it really can't do those > >> operations? > > > > interrupt handlers as of request_irq() are forced-threaded on RT so you > > can do kmalloc()/ kfree() there. smp_call_function.*() on the other hand > > are not threaded and invoked directly within the IRQ context. > > Makes sense, thanks. > > So how comes rcutorture wasn't deadlocking on RT already, is it (or RCU > itself) doing anything differently there that avoids the kfree() from > smp_call_function() handler? This was scftorture rather than rcutorture. While I know of others who regularly run rcutorture, to the best of my knowledge I am the only one who ever runs scftorture, which tests smp_call_function(), its friends, and its diagnostics. Thanx, Paul