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[124.209.188.1]) by smtp.gmail.com with ESMTPSA id d9-20020a170902aa8900b001a1d7329235sm427500plr.234.2023.03.30.20.42.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Mar 2023 20:42:15 -0700 (PDT) Date: Fri, 31 Mar 2023 12:42:09 +0900 From: Sergey Senozhatsky To: Linus Torvalds Cc: Peter Zijlstra , Petr Mladek , Sergey Senozhatsky , Luis Chamberlain , david@redhat.com, patches@lists.linux.dev, linux-modules@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, petr.pavlu@suse.com, prarit@redhat.com, gregkh@linuxfoundation.org, rafael@kernel.org, christophe.leroy@csgroup.eu, tglx@linutronix.de, song@kernel.org, rppt@kernel.org, willy@infradead.org, vbabka@suse.cz, mhocko@suse.com, dave.hansen@linux.intel.com Subject: Re: [PATCH 4/7] sempahore: add a helper for a concurrency limiter Message-ID: <20230331034209.GA12892@google.com> References: <20230329053149.3976378-1-mcgrof@kernel.org> <20230329053149.3976378-5-mcgrof@kernel.org> <20230329072112.GG4253@hirez.programming.kicks-ass.net> <20230329091935.GP4253@hirez.programming.kicks-ass.net> <20230330115626.GA124812@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam03 X-Stat-Signature: p19n3nnjzety9bkxgifjxtofrxxwk7oi X-Rspamd-Queue-Id: 9EF3514000B X-HE-Tag: 1680234137-566911 X-HE-Meta: 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 FxPrwS/z RpifLQdxS5N1JeZFfHpTJUmpym6TIdYWq/2FZthy2Q+nSCGVnKgVaL3L/P/XKH5qb9S7/Rh5tJ1K7CSt6dimcNuXkcHROrNATyLKfpsF9hl7wcg/kfQGyNImGWWeZ92ADbpCVTRaDB4TcdIlGVQhSGNwv5vjkuX5Od9n+x478N4ymJHWF4Nwe+zbh8B2BhKllo46IuOuJLMJg7ga7RbTRdzoQx1d3x0ahav2oiktP0rQfp+5HiDTWM5BdCcTXkVCx2B94bRkjm0YuDd+gfavrcAX6kZ409GbKbRJF98qJeFi9HJfzx7dyHQrmKSGRyI+xXn4QFxDndlsg45E= 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 (23/03/30 09:23), Linus Torvalds wrote: > Although we also do have some other issues - I think down_trylock() is > ok in irq contexts, but mutex_trylock() is not. Maybe that's why > printk uses semaphores? I forget. Yes, correct. IIRC we also cannot safely call mutex_unlock() from IRQ context because it takes some internal mutex spin_lock in a non-IRQ-safe manner. Semaphore is OK in this regard, both semaphore try_lock() and unlock() can be called from IRQ.