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 EA1CF2DCBF0; Mon, 26 May 2025 03:03:45 +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=1748228626; cv=none; b=PXsnJ3GmvSOcroCPu3b3Vpeell2oep/iDfnntBqH9FgJG8MMbkEhqrqmHUCmZnBuOADqa42CnXLbej+Bsg7cj5HaYWAYdR9uNegs4kgE1S3yermyLxqZyzt88+OX3wy5t+F0xhhMHLhJ3IE6wEs3wGwkqn1s1DjRSLmk4ofcDSo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748228626; c=relaxed/simple; bh=Wv86JuCfVaaJ8z4khY3hTwzcVnR1Opi+FwW14hAOfdM=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=XogVDkB0Nvp69viKI1nEHgZOpYCRFyjmeok1nkPAjj86hralivWCHtdubIUcjcs5XnHjPQKGN2sR5/fHdXr68YhICaXCt3QK1iaouGyNVWqaQ2a13imUvQM4A58gix6iy14DchH52DHwpZD6qTUWQqnvIwrMsOygOga5POlu/hA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=YOdYL3yf; 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="YOdYL3yf" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 80AE3C4CEEA; Mon, 26 May 2025 03:03:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1748228625; bh=Wv86JuCfVaaJ8z4khY3hTwzcVnR1Opi+FwW14hAOfdM=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=YOdYL3yfnBQBsvhZNe3bBnw5EIVCFOHgvNRwOCPIplLMqWr5pXZwI6tBz4s4IuZmK q2AFU9ruTiwiDWXa89pCc5FxqhZKI5QL447FSBzpaXuMd/aaajvLDjjP13lJoDEHZq qsQUnF4qM+dsy01jCeD+mTgKgLSCBllol9y2M3PIukshL5rxl3qYSaofTN6YR23f+1 +qSKqUBxJMBBTwQ/2mkL4Yr+TzF+LcvIWhIlkwj5bnrL2BqXLbFLPwjIwGts4uX2WR dDYvmEn6ARJqB1ZRZncI8v6UHsp7y0vVYbBM+AvxTBa4EQLBt94IdmlSMgSDBzqRSq oytwSmgUfHEJg== Date: Mon, 26 May 2025 12:03:42 +0900 From: Masami Hiramatsu (Google) To: Steven Rostedt Cc: Mathieu Desnoyers , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Subject: Re: [PATCH v3 1/2] tracing: ring_buffer: Rewind persistent ring buffer when reboot Message-Id: <20250526120342.cdcfca9ac3c2161d48c03af5@kernel.org> In-Reply-To: <20250523172857.02ab4a75@gandalf.local.home> References: <174792927500.496143.10668210464102033012.stgit@mhiramat.tok.corp.google.com> <174792928413.496143.17979267710069360561.stgit@mhiramat.tok.corp.google.com> <20250523165425.0275c9a1@gandalf.local.home> <20250523172857.02ab4a75@gandalf.local.home> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Fri, 23 May 2025 17:28:57 -0400 Steven Rostedt wrote: > On Fri, 23 May 2025 16:54:25 -0400 > Steven Rostedt wrote: > > > I think we also need this: > > > > diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c > > index 7d837963dd1e..456efebc396a 100644 > > --- a/kernel/trace/ring_buffer.c > > +++ b/kernel/trace/ring_buffer.c > > @@ -3638,6 +3638,9 @@ rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer, > > > > rb_reset_tail(cpu_buffer, tail, info); > > > > + /* The new page should have zero committed */ > > + rb_init_page(next_page->page); > > + > > /* Commit what we have for now. */ > > rb_end_commit(cpu_buffer); > > /* rb_end_commit() decs committing */ > > No we don't need it ;-) > > I'm looking deeper into the code and we have this: > > /* > * No need to worry about races with clearing out the commit. > * it only can increment when a commit takes place. But that > * only happens in the outer most nested commit. > */ > local_set(&next_page->page->commit, 0); > > When the tail page gets moved. Yeah, when the page gets written, it is cleared. Thanks, > > -- Steve -- Masami Hiramatsu (Google)