[lkml]   [2008]   [Feb]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
Patch in this message
SubjectRe: [PATCH] Remove never-migrates assumption from rcu_process_callbacks()

* Paul E. McKenney <> wrote:

> Hello again!
> This patch fixes a potentially invalid access to a per-CPU variable in
> rcu_process_callbacks(). This per-CPU access needs to be done in such
> a way as to guarantee that the code using it cannot move to some other
> CPU before all uses of the value accessed have completed. Even though
> this code is currently only invoked from softirq context, which
> currrently cannot migrate to some other CPU, life would be better if
> this code did not silently make such an assumption.

i've got the patch below queued up already - same thing, right?


Subject: rcupreempt: fix hibernate/resume in presence of PREEMPT_RCU and hotplug
From: "Paul E. McKenney" <>
Date: Wed, 27 Feb 2008 16:21:10 -0800

This fixes a oops encountered when doing hibernate/resume in presence
of PREEMPT_RCU. The problem was that the code failed to disable preemption
when accessing a per-CPU variable. This is OK when called from code
that already has preemption disabled, but such is not the case from
the suspend/resume code path.

Reported-by: Dave Young <>
Tested-by: Dave Young <>
Signed-off-by: Paul E. McKenney <>
Signed-off-by: Ingo Molnar <>
kernel/rcupreempt.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

Index: linux/kernel/rcupreempt.c
--- linux.orig/kernel/rcupreempt.c
+++ linux/kernel/rcupreempt.c
@@ -918,8 +918,9 @@ void rcu_offline_cpu(int cpu)
* fix.

+ local_irq_save(flags);
rdp = RCU_DATA_ME();
- spin_lock_irqsave(&rdp->lock, flags);
+ spin_lock(&rdp->lock);
*rdp->nexttail = list;
if (list)
rdp->nexttail = tail;

 \ /
  Last update: 2008-02-28 21:03    [W:0.094 / U:0.336 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site