Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752332AbZK3Iw4 (ORCPT ); Mon, 30 Nov 2009 03:52:56 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751383AbZK3Iw4 (ORCPT ); Mon, 30 Nov 2009 03:52:56 -0500 Received: from smtp.nokia.com ([192.100.105.134]:40104 "EHLO mgw-mx09.nokia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751060AbZK3Iwz (ORCPT ); Mon, 30 Nov 2009 03:52:55 -0500 Subject: Re: [PATCH/RFC v5 4/5]: core: Add dump device to call on oopses and panics From: Artem Bityutskiy Reply-To: dedekind1@gmail.com To: =?ISO-8859-1?Q?J=F6rn?= Engel Cc: Simon Kagstrom , Linus Torvalds , linux-mtd , LKML , "Koskinen Aaro (Nokia-D/Helsinki)" , Ingo Molnar , David Woodhouse , Andrew Morton , Alan Cox In-Reply-To: <20091130074603.GA30911@logfs.org> References: <20091012131528.GC25464@elte.hu> <20091012153937.0dcd73e5@marrow.netinsight.se> <20091012110954.67d7d8d8.akpm@linux-foundation.org> <20091012182346.GH17138@elte.hu> <20091013151751.59e217a7@marrow.netinsight.se> <20091013152235.188059d2@marrow.netinsight.se> <20091126093657.GA25430@logfs.org> <1259566071.7518.48.camel@localhost> <20091130074603.GA30911@logfs.org> Content-Type: text/plain; charset="UTF-8" Date: Mon, 30 Nov 2009 10:51:58 +0200 Message-Id: <1259571118.7518.56.camel@localhost> Mime-Version: 1.0 X-Mailer: Evolution 2.26.3 (2.26.3-1.fc11) Content-Transfer-Encoding: 8bit X-OriginalArrivalTime: 30 Nov 2009 08:52:04.0927 (UTC) FILETIME=[63F344F0:01CA719A] X-Nokia-AV: Clean Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3215 Lines: 113 On Mon, 2009-11-30 at 08:46 +0100, Jörn Engel wrote: > On Mon, 30 November 2009 09:27:51 +0200, Artem Bityutskiy wrote: > > > > To me it looks like 'log_end' is not supposed to wrap. What makes you > > think it can? In which cases it can? > > It is a 32bit variable. Would do you expect happens once you reach > 0xffffffff and add 1? Yes, now I see log_end is an ever increasing variable. How about this patch on top of the existing one (untested): diff --git a/kernel/printk.c b/kernel/printk.c index f711b99..66995ca 100644 --- a/kernel/printk.c +++ b/kernel/printk.c @@ -1486,28 +1486,27 @@ static const char *kmsg_to_str(enum kmsg_dump_reason reason) */ void kmsg_dump(enum kmsg_dump_reason reason) { - unsigned long len = ACCESS_ONCE(log_end); + unsigned long end = ACCESS_ONCE(log_end) & LOG_BUF_MASK; struct kmsg_dumper *dumper; const char *s1, *s2; unsigned long l1, l2; unsigned long flags; - s1 = ""; - l1 = 0; - s2 = log_buf; - l2 = len; - - /* Have we rotated around the circular buffer? */ - if (len > log_buf_len) { - unsigned long pos = len & LOG_BUF_MASK; - - s1 = log_buf + pos; - l1 = log_buf_len - pos; - - s2 = log_buf; - l2 = pos; + /* + * Have we ever rotated around the circular buffer? If we never did, + * we have to have zeroes at the end. + */ + if (log_buf[end]) { + s1 = log_buf + end; + l1 = log_buf_len - end; + } else { + s1 = ""; + l1 = 0; } + s2 = log_buf; + l2 = end; + if (!spin_trylock_irqsave(&dump_list_lock, flags)) { printk(KERN_ERR "dump_kmsg: dump list lock is held during %s, skipping dump\n", kmsg_to_str(reason)); Then the whole function will look like this: /** * kmsg_dump - dump kernel log to kernel message dumpers. * @reason: the reason (oops, panic etc) for dumping * * Iterate through each of the dump devices and call the oops/panic * callbacks with the log buffer. */ void kmsg_dump(enum kmsg_dump_reason reason) { unsigned long end = ACCESS_ONCE(log_end) & LOG_BUF_MASK; struct kmsg_dumper *dumper; const char *s1, *s2; unsigned long l1, l2; unsigned long flags; /* * Have we ever rotated around the circular buffer? If we never did, * we have to have zeroes at the end. */ if (log_buf[end]) { s1 = log_buf + end; l1 = log_buf_len - end; } else { s1 = ""; l1 = 0; } s2 = log_buf; l2 = end; if (!spin_trylock_irqsave(&dump_list_lock, flags)) { printk(KERN_ERR "dump_kmsg: dump list lock is held during %s, skipping dump\n", kmsg_to_str(reason)); return; } list_for_each_entry(dumper, &dump_list, list) dumper->dump(dumper, reason, s1, l1, s2, l2); spin_unlock_irqrestore(&dump_list_lock, flags); } -- Best Regards, Artem Bityutskiy (Артём Битюцкий) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/