linux-kernel - 3.0.23-rt39 BUG: scheduling while atomic, _cpu

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 9 Mar 2012 17:51:50 -0800
From:	Frank Rowand <frank.rowand@...sony.com>
To:	<tglx@...utronix.de>, <rostedt@...dmis.org>
CC:	<linux-kernel@...r.kernel.org>, <linux-rt-users@...r.kernel.org>
Subject: 3.0.23-rt39 BUG: scheduling while atomic, _cpu_down()

Hi Thomas,
(and Steve, since you've been mucking about in the hotplug code,)

Yet another bit of fallout related to hotplug.

This appears to affect 3.0-rt1, 3.0.23-rt29, and 3.2.9-rt17.
(Thus probably all 3.x versions, but I haven't been masochistic
enough to check.)

If not defined CONFIG_PREEMPT_RT_FULL then

  - hotplug_lock() is a mutex_lock()
  - cpu_hotplug_begin() calls hotplug_lock()
  - _cpu_down() calls cpu_hotplug_begin() with preemption
    disabled (disabled by the migrate_disable())

The call to cpu_hotplug_begin() is not in a preempt disabled
region until hotplug-use-migrate-disable.patch.  This patch
moves the preempt_enable() (aka migrate_enable()) from just
before calling cpu_hotplug_begin() to after "out_cancel:".

The BUG can be triggered by:

   echo 0 > /sys/devices/system/cpu/cpu1/online 

-Frank

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/