linux-kernel - Re: [linux-pm] [PATCH] [suspend] pci_raw_set_power_state: replace msleep by udelay in resuming procedure

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Message-ID: <Pine.LNX.4.44L0.0907161259510.2952-100000@iolanthe.rowland.org>
Date:	Thu, 16 Jul 2009 13:02:53 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Wu Zhangjin <wuzhangjin@...il.com>
cc:	linux-pm@...ts.linux-foundation.org, <len.brown@...el.com>,
	<yanh@...ote.com>, <linux-kernel@...r.kernel.org>,
	<wuzj@...ote.com>, <zhangfx@...ote.com>
Subject: Re: [linux-pm] [PATCH] [suspend] pci_raw_set_power_state: replace
 msleep by udelay in resuming procedure

On Thu, 16 Jul 2009, Wu Zhangjin wrote:

> we can not call msleep() when resuming from STR/Standby: if the
> current_state of the pci device is PCI_D3hot, means we are in the
> procedure of resuming, in this procedure, we can not re-schedule,
> otherwise, there will be a deadlock.

I don't understand.

First of all, why does current_state == PCI_D3hot mean the system is
resuming from sleep?  Isn't it possible that the PCI device is going
through a runtime resume?

Secondly, why will scheduling during a resume cause a deadlock?

Alan Stern

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