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Thu, 21 Nov 2024 07:35:23 -0800 (PST) MIME-Version: 1.0 References: <20241028010818.2487581-1-andrii@kernel.org> <20241028010818.2487581-2-andrii@kernel.org> <20241121124011.GK24774@noisy.programming.kicks-ass.net> In-Reply-To: <20241121124011.GK24774@noisy.programming.kicks-ass.net> From: Suren Baghdasaryan Date: Thu, 21 Nov 2024 07:35:12 -0800 Message-ID: Subject: Re: [PATCH v4 tip/perf/core 1/4] mm: Convert mm_lock_seq to a proper seqcount To: Peter Zijlstra Cc: Andrii Nakryiko , linux-trace-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, oleg@redhat.com, rostedt@goodmis.org, mhiramat@kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, jolsa@kernel.org, paulmck@kernel.org, willy@infradead.org, mjguzik@gmail.com, brauner@kernel.org, jannh@google.com, mhocko@kernel.org, vbabka@suse.cz, shakeel.butt@linux.dev, hannes@cmpxchg.org, Liam.Howlett@oracle.com, lorenzo.stoakes@oracle.com, david@redhat.com, arnd@arndb.de, richard.weiyang@gmail.com, zhangpeng.00@bytedance.com, linmiaohe@huawei.com, viro@zeniv.linux.org.uk, hca@linux.ibm.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: BCF64A001E X-Stat-Signature: u7dsbrmz37zdeubwfmdqbu8ogwfeinb7 X-Rspam-User: X-HE-Tag: 1732203287-560786 X-HE-Meta: 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 gKDa7JoD j+ZbW7kibNNConKHzJU+3GmzvdCvzfOEB2D5lNBnDkgFQ1wIQFe/fp4i9bujvge/NqakXPtUCN/gZIMUTubS8BCMq+JsQy9bnKxe8b8EOWDANk6DhZ6Lcm9EkeBFFCpB6WggFv+ckh3/wt/6UXdWHpYR1vmkVJqzcm9tbdxNnZlL6x1UymilkVuRiyiuew441XT+PVE+UoVAfzPtkt64i/iLsfN4AMKgVguKKE3/611o3xLrXZ9I6pUm4POK9hDhl/SbHqSFHWAOSSzdxUlg2noldxPE5RqXWUY7wzTXvtLPW6kOP+WttieW9Wbyp98BuqEqwwYJoKV/KmDggppc3cYZNe9sjEMNjhbicIk8Dj5eiPL3VH3tz7zM0SA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000002, 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, Nov 21, 2024 at 4:40=E2=80=AFAM Peter Zijlstra wrote: > > On Sun, Oct 27, 2024 at 06:08:15PM -0700, Andrii Nakryiko wrote: > > +/* > > + * Drop all currently-held per-VMA locks. > > + * This is called from the mmap_lock implementation directly before re= leasing > > + * a write-locked mmap_lock (or downgrading it to read-locked). > > + * This should normally NOT be called manually from other places. > > + * If you want to call this manually anyway, keep in mind that this wi= ll release > > + * *all* VMA write locks, including ones from further up the stack. > > + */ > > +static inline void vma_end_write_all(struct mm_struct *mm) > > +{ > > + mmap_assert_write_locked(mm); > > + /* > > + * Nobody can concurrently modify mm->mm_lock_seq due to exclusiv= e > > + * mmap_lock being held. > > + */ > > You can write: > > ASSERT_EXCLUSIVE_WRITER(mm->mm_lock_seq); > > instead of that comment. Then KCSAN will validate the claim. Thanks for the tip! This one looks not critical but I see there are more important comments in "mm: Introduce mmap_lock_speculation_{begin|end}". I'll send a new version shortly. > > > + mm_lock_seqcount_end(mm); > > +}