From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A567D2D323D for ; Tue, 22 Jul 2025 08:11:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753171900; cv=none; b=fY42zs7JfzKFc95PbhkeX7wwoWxZneUv9RdJsHeDXAlpKD6nweP+76cmNrea0DYPm0cQ87V7rq10CGUcvR85RHqbe2uvAj1/xnHhh6Jr94VM8ZBehZ1/V5KrqusrE5qmLcv2COb03RZdDNU01lfAosObL1qAsNereo7HMtBtJ5o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753171900; c=relaxed/simple; bh=PF8Pr1kD174b7Zl7PPDZkkSbVuADD9FN3Ng9KvlN52U=; h=Message-ID:Date:MIME-Version:Subject:To:References:From: In-Reply-To:Content-Type; b=ru9vAdxIVlPvw7Jni/N2nhVMEoUxhS5jpHYVyOChpHBvGbwVk2Q3QgU3X/Ak7PUsE/Fzpq5DoEDFbU19Lsl5NR57Ri9e/MJoR+OWr8sDlqWydyr8W7b1Vk2U4GLqqA+pBBKVHATKMFLi29aiSCSdg5svDBLLjYI+wGhNpRBHiiQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=kfby9Pdb; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="kfby9Pdb" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 73BFBC4CEEB; Tue, 22 Jul 2025 08:11:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1753171900; bh=PF8Pr1kD174b7Zl7PPDZkkSbVuADD9FN3Ng9KvlN52U=; h=Date:Subject:To:References:From:In-Reply-To:From; b=kfby9PdbX8yo7/yXcHSf1UMjfcBxZ2RNmWCUSqsKMLhXX+1UeSEf5R9+NvIZYredS t2yY4XJksPqGPk3z2Gqpn5YRq+q/judf7D+c+aefEYeqLi9e2Tm2GfDki6RJ2ORx6f H3l41iifgiH2zwF9ggRpccXeOXKSfSR+Fjbdp89b0aGv/C40cVMh7Z89ujtoS+k0LF 0hN9dyHnxTYMlk/jpNIu7rv+uB40ZkaQSVQyXhKInhZiakwtGjer18LjLFTMcigxmM 2R3U6EZBU/6VjOdyzYnLbmlGnuV4nvZG6XVo6vATzATszZmmM8QluDATQYPDVSp4lJ eIdN2zZdjdbjQ== Message-ID: <7eb73676-7f65-4eb5-8735-559eff73e1cf@kernel.org> Date: Tue, 22 Jul 2025 10:11:38 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] irq: simplify irq_im_handle_irq() To: Yury Norov , Thomas Gleixner , linux-kernel@vger.kernel.org References: <20250719211818.402115-1-yury.norov@gmail.com> Content-Language: en-US From: Jiri Slaby Autocrypt: addr=jirislaby@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 19. 07. 25, 23:18, Yury Norov wrote: > From: Yury Norov (NVIDIA) > > Hi Thomas, This does not belong to a commit log ^^. > The function calls bitmap_empty() for potentially every bit in > work_ctx->pending, which makes a simple bitmap traverse O(N^2). > Fix it by switching to the dedicated for_each_set_bit(). Looks good. > While there, fix using atomic clear_bit() in a context where atomicity > cannot be guaranteed. What does this mean? __clear_bit() can corrupt the bitmap when there is an in-flight set_bit(), right? > Signed-off-by: Yury Norov (NVIDIA) > --- > kernel/irq/irq_sim.c | 8 +++----- > 1 file changed, 3 insertions(+), 5 deletions(-) > > diff --git a/kernel/irq/irq_sim.c b/kernel/irq/irq_sim.c > index ae4c9cbd1b4b..e05904da7e3d 100644 > --- a/kernel/irq/irq_sim.c > +++ b/kernel/irq/irq_sim.c > @@ -128,15 +128,13 @@ static struct irq_chip irq_sim_irqchip = { > static void irq_sim_handle_irq(struct irq_work *work) > { > struct irq_sim_work_ctx *work_ctx; > - unsigned int offset = 0; > + unsigned int offset; > int irqnum; > > work_ctx = container_of(work, struct irq_sim_work_ctx, work); > > - while (!bitmap_empty(work_ctx->pending, work_ctx->irq_count)) { > - offset = find_next_bit(work_ctx->pending, > - work_ctx->irq_count, offset); > - clear_bit(offset, work_ctx->pending); > + for_each_set_bit(offset, work_ctx->pending, work_ctx->irq_count) { > + __clear_bit(offset, work_ctx->pending); > irqnum = irq_find_mapping(work_ctx->domain, offset); > handle_simple_irq(irq_to_desc(irqnum)); > } -- js suse labs