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McKenney" Cc: Michal Hocko , Thomas Gleixner , Uladzislau Rezki , LKML , RCU , linux-mm@kvack.org, Andrew Morton , Vlastimil Babka , Matthew Wilcox , "Theodore Y . Ts'o" , Joel Fernandes , Sebastian Andrzej Siewior , Oleksiy Avramchenko Subject: Re: [RFC-PATCH 1/2] mm: Add __GFP_NO_LOCKS flag Message-ID: <20200813183121.GY2674@hirez.programming.kicks-ass.net> References: <20200813095840.GA25268@pc636> <874kp6llzb.fsf@nanos.tec.linutronix.de> <20200813133308.GK9477@dhcp22.suse.cz> <87sgcqty0e.fsf@nanos.tec.linutronix.de> <20200813145335.GN9477@dhcp22.suse.cz> <20200813154159.GR4295@paulmck-ThinkPad-P72> <20200813155412.GP9477@dhcp22.suse.cz> <20200813160442.GV4295@paulmck-ThinkPad-P72> <20200813161357.GQ9477@dhcp22.suse.cz> <20200813162904.GX4295@paulmck-ThinkPad-P72> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200813162904.GX4295@paulmck-ThinkPad-P72> X-Rspamd-Queue-Id: 1D383180D0185 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Aug 13, 2020 at 09:29:04AM -0700, Paul E. McKenney wrote: > OK. So the current situation requires a choice between these these > alternatives, each of which has shortcomings that have been mentioned > earlier in this thread: > > 1. Prohibit invoking allocators from raw atomic context, such > as when holding a raw spinlock. This! This has always been the case, why are we even considering change here? > 2. Adding a GFP_ flag. The patch 1/2 in this thread is horrendous crap. > 3. Reusing existing GFP_ flags/values/whatever to communicate > the raw-context information that was to be communicated by > the new GFP_ flag. > > 4. Making lockdep forgive acquiring spinlocks while holding > raw spinlocks, but only in CONFIG_PREEMPT_NONE=y kernels. > > Am I missing anything? How would 4 solve anything? In other words, what is the actual friggin problem? I've not seen one described anywhere.