From mboxrd@z Thu Jan 1 00:00:00 1970 From: Suzuki K Poulose Subject: Re: [PATCH 09/30] coresight: cpu-debug: Replace mutex with mutex_trylock on panic notifier Date: Thu, 28 Apr 2022 09:11:10 +0100 Message-ID: <3cafe4fd-8a0b-2633-44a3-2995abd6c38c@arm.com> References: <20220427224924.592546-1-gpiccoli@igalia.com> <20220427224924.592546-10-gpiccoli@igalia.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20220427224924.592546-10-gpiccoli-wEGTBA9jqPzQT0dZR+AlfA@public.gmane.org> List-ID: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: "Guilherme G. Piccoli" , akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, bhe-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, pmladek-IBi9RG/b67k@public.gmane.org, kexec-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, bcm-kernel-feedback-list-dY08KVG/lbpWk0Htik3J/w@public.gmane.org, coresight-cunTk1MwBs8s++Sfvej+rw@public.gmane.org, linuxppc-dev-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org, linux-alpha-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, linux-edac-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-hyperv-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-leds-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mips-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-parisc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-pm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-remoteproc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-s390-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-um-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, linux-xtensa-PjhNF2WwrV/0Sa2dR60CXw@public.gmane.org, netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, openipmi-developer-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org, rcu-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, sparclinux-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, xen-devel-GuqFBffKawtpuQazS67q72D2FQJk+8+b@public.gmane.org, x86-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, kernel-dev-wEGTBA9jqPzQT0dZR+AlfA@public.gmane.org, kernel-WeLdAqEWwDvk1uMJSBkQmQ@public.gmane.org, halves-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org, fabiomirmar-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, alejandro.j.jimenez@ora Hi Guilherme, On 27/04/2022 23:49, Guilherme G. Piccoli wrote: > The panic notifier infrastructure executes registered callbacks when > a panic event happens - such callbacks are executed in atomic context, > with interrupts and preemption disabled in the running CPU and all other > CPUs disabled. That said, mutexes in such context are not a good idea. > > This patch replaces a regular mutex with a mutex_trylock safer approach; > given the nature of the mutex used in the driver, it should be pretty > uncommon being unable to acquire such mutex in the panic path, hence > no functional change should be observed (and if it is, that would be > likely a deadlock with the regular mutex). > > Fixes: 2227b7c74634 ("coresight: add support for CPU debug module") > Cc: Leo Yan > Cc: Mathieu Poirier > Cc: Mike Leach > Cc: Suzuki K Poulose > Signed-off-by: Guilherme G. Piccoli How would you like to proceed with queuing this ? I am happy either way. In case you plan to push this as part of this series (I don't see any potential conflicts) : Reviewed-by: Suzuki K Poulose