Commit-ID: 92c38702e98e58438c3760ebb279c40bbca8bd5f
Gitweb: http://git.kernel.org/tip/92c38702e98e58438c3760ebb279c40bbca8bd5f
Author: Paul E. McKenney <paul.mckenney@xxxxxxxxxx>
AuthorDate: Mon, 16 Apr 2012 12:12:09 -0700
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Tue, 17 Apr 2012 07:30:54 -0700
rcu: Permit call_rcu() from CPU_DYING notifiers
As of:
29494be71afe ("rcu,cleanup: simplify the code when cpu is dying")
RCU adopts callbacks from the dying CPU in its CPU_DYING notifier,
which means that any callbacks posted by later CPU_DYING notifiers
are ignored until the CPU comes back online.
A WARN_ON_ONCE() was added to __call_rcu() by:
e56014000816 ("rcu: Simplify offline processing")
to check for this condition. Although this condition did not trigger
(at least as far as I know) during -next testing, it did recently
trigger in mainline:
https://lkml.org/lkml/2012/4/2/34
What is needed longer term is for RCU's CPU_DEAD notifier to adopt any
callbacks that were posted by CPU_DYING notifiers, however, the Linux
kernel has been running with this sort of thing happening for quite
some time. So the only thing that qualifies as a regression is the
WARN_ON_ONCE(), which this commit removes.
Making RCU's CPU_DEAD notifier adopt callbacks posted by CPU_DYING
notifiers is a topic for the 3.5 release of the Linux kernel.
Reported-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
Signed-off-by: Paul E. McKenney <paul.mckenney@xxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
---
kernel/rcutree.c | 1 -
1 files changed, 0 insertions(+), 1 deletions(-)
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 1050d6d..d0c5baf 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1820,7 +1820,6 @@ __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu),
* a quiescent state betweentimes.
*/
local_irq_save(flags);
- WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
rdp = this_cpu_ptr(rsp->rda);
/* Add the callback to our list. */
--
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