From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id CF989C77B60 for ; Fri, 31 Mar 2023 03:42:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229902AbjCaDmU (ORCPT ); Thu, 30 Mar 2023 23:42:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47912 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229840AbjCaDmR (ORCPT ); Thu, 30 Mar 2023 23:42:17 -0400 Received: from mail-pj1-x102c.google.com (mail-pj1-x102c.google.com [IPv6:2607:f8b0:4864:20::102c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E90A8CC36 for ; Thu, 30 Mar 2023 20:42:16 -0700 (PDT) Received: by mail-pj1-x102c.google.com with SMTP id j13so19209328pjd.1 for ; Thu, 30 Mar 2023 20:42:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; t=1680234136; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=D2yoA6/ZMAiU5n58XnU5GRn99au0wJfFSmiuyy5JMiA=; b=l2BgSx22kuf8Hs3D7qJk6EE10cDBOjYG0ia03DbUz+keXgFSqQ0kOnwuvFo1mqJ7e8 sr2sOplzSkPKNkE9f69WVC7cUXhYU+E/lJhlnq9gDVmZxBMPX8IDgw7cLxCFn7kC+pdl eP+vfO5qQh+5YySDiX2/XfMPhhzlNGGAVojJE= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1680234136; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=D2yoA6/ZMAiU5n58XnU5GRn99au0wJfFSmiuyy5JMiA=; b=kYBdy49Qf9qKQ8Tm+LR6IeT4Zc3VcLCZ1pPOTsOH5H4Zcm5VxeIt/ExX8tdKo1KrNZ F9WDcp5co1JblLCLF3nSTz0B7vbFawJhh63+PonoAD/1ppeWjAuvURMzL33H6xsUIQqG tj+rxHMm7BQ5I2Jniv79EU/RISZMcUgpEeXP/ndWUxNXxnjQVWmEcesVB18n87anaywa lCCFrc8JTrDHGJVbZcNtyeMmhGjXr534jhgti2Ewbzdqf/uGPK7pHE7w3CwjzMfe7t+x v+3I9CmHu025mZNRA4zwBTanEWzXPXCqQ/S4jTHTxJUt3OLD8+rsE64Fqac05wtGP/g9 SS9w== X-Gm-Message-State: AAQBX9dMJVksZoeOu63M+8jfsXs/tjIKIweq3UUzdHq9g+i0DMQ816FQ 1NBR3XUfeZpt6lvX6byzphBoRw== X-Google-Smtp-Source: AKy350YEadHnIPucAgMaeBL0HMKusS65/ZM2KAeXc/wd10yIBt72Hu/asTJYkl9H5ZaueGU8YrY2TA== X-Received: by 2002:a17:903:230d:b0:1a1:9787:507d with SMTP id d13-20020a170903230d00b001a19787507dmr9866306plh.3.1680234136348; Thu, 30 Mar 2023 20:42:16 -0700 (PDT) Received: from google.com (KD124209188001.ppp-bb.dion.ne.jp. [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: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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.