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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CCAFDC433EF for ; Wed, 27 Oct 2021 15:48:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A5E45610A3 for ; Wed, 27 Oct 2021 15:48:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242836AbhJ0PvL (ORCPT ); Wed, 27 Oct 2021 11:51:11 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:41318 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242827AbhJ0PvJ (ORCPT ); Wed, 27 Oct 2021 11:51:09 -0400 From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1635349723; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=tkgVdeXd598pY6QU8+NQfjeQPsQIGyv6eN0Glc1LxB8=; b=E1mttTQNJGFfAAYzAmlbyJlajz+M1aCHTFA0exSqMApNuSblDEJ/VWVzbUiib9QPsnIDSG bqG1p6eHKr32gHH7LUa8Q6gm7GWXtBCoano7f85qDMZU6wimszeQAUxkgoVmuWymqt5g9+ gkB/aJR5hqmxLjaG+ud4Pmh8pBFBoy8wObsI0NagaE90M1vtHKn/OSm+1id6atWiPHy3qE 2jAwkoPAuPLantUo940hSj8BskMyWLcoR12DuYwbcAvPhGg/FAXm8Yu1iq9MGl6r/Wvxch SgG9+XVztZfP6u1CV2he2FKpjLX92dXO5RKZBwYEhoKMj/xOElRmQqeo5QtsVQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1635349723; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=tkgVdeXd598pY6QU8+NQfjeQPsQIGyv6eN0Glc1LxB8=; b=vFfC/cCfKpiBQYOBxRqi7Tsb/O51LcCf3i/k0yyiJi6iXtBd7cWNLp5srPz34r7Ueikskh GZvvGnQTSpWHdTCw== To: Petr Mladek Cc: "chunlei.wang" , Sergey Senozhatsky , Steven Rostedt , Matthias Brugger , linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] printk: ringbuffer: Improve prb_next_seq() performance In-Reply-To: References: Date: Wed, 27 Oct 2021 17:54:42 +0206 Message-ID: <875ytih3j9.fsf@jogness.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021-10-27, Petr Mladek wrote: > diff --git a/kernel/printk/printk_ringbuffer.c b/kernel/printk/printk_ringbuffer.c > index 8a7b7362c0dd..24f47fbefbb5 100644 > --- a/kernel/printk/printk_ringbuffer.c > +++ b/kernel/printk/printk_ringbuffer.c > @@ -474,8 +474,10 @@ static enum desc_state desc_read(struct prb_desc_ring *desc_ring, > * state has been re-checked. A memcpy() for all of @desc > * cannot be used because of the atomic_t @state_var field. > */ > - memcpy(&desc_out->text_blk_lpos, &desc->text_blk_lpos, > - sizeof(desc_out->text_blk_lpos)); /* LMM(desc_read:C) */ > + if (desc_out) { > + memcpy(&desc_out->text_blk_lpos, &desc->text_blk_lpos, > + sizeof(desc_out->text_blk_lpos)); /* LMM(desc_read:C) */ > + } > if (seq_out) > *seq_out = info->seq; /* also part of desc_read:C */ > if (caller_id_out) You also need this hunk: @@ -530,7 +530,8 @@ static enum desc_state desc_read(struct prb_desc_ring *desc_ring, state_val = atomic_long_read(state_var); /* LMM(desc_read:E) */ d_state = get_desc_state(id, state_val); out: - atomic_long_set(&desc_out->state_var, state_val); + if (desc_out) + atomic_long_set(&desc_out->state_var, state_val); return d_state; } Sorry, I missed it in my last review. This time I build+boot tested the patch. With this hunk added: Reviewed-by: John Ogness John