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Piccoli" In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-3.0 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,T_SCC_BODY_TEXT_LINE,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/05/2022 09:14, Petr Mladek wrote: > [...] >> With that said, it's dangerous to use regular spinlocks in such path, >> as introduced by commit b3c0f8774668 ("misc/pvpanic: probe multiple instances"). >> This patch fixes that by replacing regular spinlocks with the trylock >> safer approach. > > It seems that the lock is used just to manipulating a list. A super > safe solution would be to use the rcu API: rcu_add_rcu() and > list_del_rcu() under rcu_read_lock(). The spin lock will not be > needed and the list will always be valid. > > The advantage would be that it will always call members that > were successfully added earlier. That said, I am not familiar > with pvpanic and am not sure if it is worth it. > >> It also fixes an old comment (about a long gone framebuffer code) and >> the notifier priority - we should execute hypervisor notifiers early, >> deferring this way the panic action to the hypervisor, as expected by >> the users that are setting up pvpanic. > > This should be done in a separate patch. It changes the behavior. > Also there might be a discussion whether it really should be > the maximal priority. > > Best Regards, > Petr Thanks for the review Petr. Patch was already merged - my goal was to be concise, i.e., a patch per driver / module, so the patch kinda fixes whatever I think is wrong with the driver with regards panic handling. Do you think it worth to remove this patch from Greg's branch just to split it in 2? Personally I think it's not worth, but opinions are welcome. About the RCU part, this one really could be a new patch, a good improvement patch - it makes sense to me, we can think about that after the fixes I guess. Cheers, Guilherme