From: Lai Jiangshan <laijs@cn.fujitsu.com>
Date: Mon, 29 Sep 2008 08:00:05 +0000 (+0800)
Subject: markers: fix unregister bug and reenter bug
X-Git-Tag: v2.6.28-rc1~78^2~60
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d74185ed27651ad8d920b37d7851306ad01f7d6f;p=pandora-kernel.git

markers: fix unregister bug and reenter bug

unregister bug:

codes using makers are typically calling marker_probe_unregister()
and then destroying the data that marker_probe_func needs(or
unloading this module). This is bug when the corresponding
marker_probe_func is still running(on other cpus),
it is using the destroying/ed data.

we should call synchronize_sched() after marker_update_probes().

reenter bug:

marker_probe_register(), marker_probe_unregister() and
marker_probe_unregister_private_data() are not reentrant safe
functions. these 3 functions release markers_mutex and then
require it again and do "entry->oldptr = old; ...", but entry->oldptr
maybe is using now for these 3 functions may reenter when markers_mutex
is released.

we use synchronize_sched() instead of call_rcu_sched() to fix
this bug. actually we can do:
"
if (entry->rcu_pending)
		rcu_barrier_sched();
"
after require markers_mutex again. but synchronize_sched()
is better and simpler. For these 3 functions are not critical path.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---

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