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Tue, 10 Jan 2023 12:58:32 +0100 (CET) Received: from localhost (localhost [127.0.0.1]) by gentwo.de (Postfix) with ESMTP id B1C18B00101; Tue, 10 Jan 2023 12:58:32 +0100 (CET) Date: Tue, 10 Jan 2023 12:58:32 +0100 (CET) From: Christoph Lameter To: Marcelo Tosatti cc: atomlin@atomlin.com, frederic@kernel.org, tglx@linutronix.de, mingo@kernel.org, peterz@infradead.org, pauld@redhat.com, neelx@redhat.com, oleksandr@natalenko.name, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v13 1/6] mm/vmstat: Add CPU-specific variable to track a vmstat discrepancy In-Reply-To: <20230105125248.772766288@redhat.com> Message-ID: References: <20230105125218.031928326@redhat.com> <20230105125248.772766288@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: E26561A0009 X-Stat-Signature: nsgyarbui3r7pp4xu43jex3pofrikcmr X-HE-Tag: 1673351914-632742 X-HE-Meta: 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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: On Thu, 5 Jan 2023, Marcelo Tosatti wrote: > +static inline void vmstat_mark_dirty(void) > +{ > + this_cpu_write(vmstat_dirty, true); > +} this_cpu_write() is intended for an per cpu atomic context. You are not using it in that way. The processor may have changed before or after and thus vmstat_dirty for another CPU may have been marked dirty. I guess this would have to be called __vmstat_mark_dirty() and be using __this_cpu_write(*) with a requirement that preemption be disabled before using this function. > +static inline void vmstat_clear_dirty(void) > +{ > + this_cpu_write(vmstat_dirty, false); > +} Same > +static inline bool is_vmstat_dirty(void) > +{ > + return this_cpu_read(vmstat_dirty); > +} This function would only work correctly if preemption is disabled. Otherwise the processor may change.