Re: [2.6.33-rc5] starting emacs makes lockdep warning

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From: "Américo Wang" <xiyou.wangcong@gmail.com>
To: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	Tavis Ormandy <taviso@google.com>, Jeff Dike <jdike@addtoit.com>,
	Julien Tinnes <jln@google.com>, Matt Mackall <mpm@selenic.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Oleg Nesterov <oleg@redhat.com>,
	Alan Cox <alan@lxorguk.ukuu.org.uk>
Subject: Re: [2.6.33-rc5] starting emacs makes lockdep warning
Date: Tue, 26 Jan 2010 16:45:57 +0800	[thread overview]
Message-ID: <2375c9f91001260045s7d01c427g64bc10f5bf4db4d@mail.gmail.com> (raw)
In-Reply-To: <20100126164018.1D59.A69D9226@jp.fujitsu.com>

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On Tue, Jan 26, 2010 at 3:45 PM, KOSAKI Motohiro<kosaki.motohiro@jp.fujitsu.com> wrote:> Hi>>> On Tue, Jan 26, 2010 at 02:01:12PM +0800, Am??rico Wang wrote:>>>> > I agree, it seems that patch is useless, since we already>> > do lock_kernel() before calling __f_setown()...>>>> What's to prevent pid from being freed under us? Â BKL won't...>> I don't understand this issue at all. so, this is stupid dumb question.> Why can't we write following code?>>> Â  Â  Â  Â  Â  Â  Â  Â enum pid_type type;> Â  Â  Â  Â  Â  Â  Â  Â struct pid *pid;> Â  Â  Â  Â  Â  Â  Â  Â if (!waitqueue_active(&tty->read_wait))> Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â tty->minimum_to_wake = 1;> Â  Â  Â  Â  Â  Â  Â  Â spin_lock_irqsave(&tty->ctrl_lock, flags);> Â  Â  Â  Â  Â  Â  Â  Â if (tty->pgrp) {> Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â pid = tty->pgrp;> Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â type = PIDTYPE_PGID;> Â  Â  Â  Â  Â  Â  Â  Â } else {> Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â pid = task_pid(current);> Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â type = PIDTYPE_PID;> Â  Â  Â  Â  Â  Â  Â  Â }> Â  Â  Â  Â  Â  Â  Â  Â get_pid(pid) Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â // insert here> Â  Â  Â  Â  Â  Â  Â  Â spin_unlock_irqrestore(&tty->ctrl_lock, flags);> Â  Â  Â  Â  Â  Â  Â  Â retval = __f_setown(filp, pid, type, 0);> Â  Â  Â  Â  Â  Â  Â  Â put_pid(pid) Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â // insert here>
Yeah, this seems reasonable for me, but not sure if this is the best fix.ÿôèº{.nÇ+‰·Ÿ®‰†+%ŠËÿ±éÝ¶\x17¥Šwÿº{.nÇ+‰·¥Š{±þG«éÿŠ{ayº\x1dÊ‡Ú™ë,j\a¢f£¢·hšïêÿ‘êçz_è®\x03(éšŽŠÝ¢j"ú\x1a¶^[m§ÿÿ¾\a«þG«éÿ¢¸?™¨èÚ&£ø§~á¶iO•æ¬z·švØ^\x14\x04\x1a¶^[m§ÿÿÃ\fÿ¶ìÿ¢¸?–I¥

next prev parent reply	other threads:[~2010-01-26  8:46 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-01-26  3:20 KOSAKI Motohiro
2010-01-26  5:25 ` Américo Wang
2010-01-26  5:37   ` KOSAKI Motohiro
2010-01-26  5:49     ` KOSAKI Motohiro
2010-01-26  6:01       ` Américo Wang
2010-01-26  6:07         ` Al Viro
2010-01-26  6:24           ` Américo Wang
2010-01-26  6:54             ` Al Viro
2010-01-26  7:45           ` KOSAKI Motohiro
2010-01-26  8:45             ` Américo Wang [this message]
2010-01-26  9:14               ` Eric W. Biederman
2010-01-26  9:32                 ` Américo Wang
2010-01-26 12:33                   ` Eric W. Biederman
2010-01-26 15:58                     ` [Patch] fix the lockdep warning in tty_fasync() Américo Wang
2010-01-27  1:09                       ` KOSAKI Motohiro
2010-01-27  1:47                         ` Greg KH
2010-01-26  6:17       ` [2.6.33-rc5] starting emacs makes lockdep warning Eric W. Biederman
2010-01-26 18:16 ` check_usage_backwards() && forwards? (Was: [2.6.33-rc5] starting emacs makes lockdep warning) Oleg Nesterov
2010-01-26 18:47   ` Peter Zijlstra
2010-01-27  2:58   ` Américo Wang
2010-01-27 13:15   ` [tip:core/urgent] lockdep: Fix check_usage_backwards() error message tip-bot for Oleg Nesterov

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