Commit caa9ee77 authored Mar 24, 2006 by Oleg Nesterov Committed by Linus Torvalds Mar 24, 2006

[PATCH] rcu_process_callbacks: don't cli() while testing ->nxtlist



__rcu_process_callbacks() disables interrupts to protect itself from
call_rcu() which adds new entries to ->nxtlist.

However we can check "->nxtlist != NULL" with interrupts enabled, we can't
get "false positives" because call_rcu() can only change this condition
from 0 to 1.

Tested with rcutorture.ko.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Dipankar Sarma <dipankar@in.ibm.com>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

parent cba9f33d

kernel/rcupdate.c

+2 −3

Original line number	Diff line number	Diff line
		@@ -416,8 +416,8 @@ static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp,
		rdp->curtail = &rdp->curlist;
		}

		local_irq_disable();
		if (rdp->nxtlist && !rdp->curlist) {
		local_irq_disable();
		rdp->curlist = rdp->nxtlist;
		rdp->curtail = rdp->nxttail;
		rdp->nxtlist = NULL;
		@@ -442,9 +442,8 @@ static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp,
		rcu_start_batch(rcp);
		spin_unlock(&rcp->lock);
		}
		} else {
		local_irq_enable();
		}

		rcu_check_quiescent_state(rcp, rdp);
		if (rdp->donelist)
		rcu_do_batch(rdp);