mirrors/linux-stable
1
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git synced 2024-10-30 08:02:30 +00:00
Code Issues Releases Wiki Activity

rcu: Add comment giving debug strategy for double call_rcu()

Browse source 
The following statement has for some reason proven non-intuitive:

	WARN_ON_ONCE(rcu_segcblist_empty(&rdp->cblist) != (count == 0));

This commit therefore adds a comment that states that this warning
usually triggers in response to a double call_rcu(), which is sort
of like a double free.  The comment also suggests building with
CONFIG_DEBUG_OBJECTS_RCU_HEAD=y to track down the double call_rcu().

Reported-by: David Howells <dhowells@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2017-10-19 14:52:41 -07:00
parent 9122caf99b
commit efd88b02bb
1 changed files with 5 additions and 0 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

5
kernel/rcu/tree.c
View file

@ -2789,6 +2789,11 @@ static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp)
rdp->n_force_qs_snap = rsp->n_force_qs; rdp->n_force_qs_snap = rsp->n_force_qs;
} else if (count < rdp->qlen_last_fqs_check - qhimark) } else if (count < rdp->qlen_last_fqs_check - qhimark)
rdp->qlen_last_fqs_check = count; rdp->qlen_last_fqs_check = count;
/*
* The following usually indicates a double call_rcu(). To track
* this down, try building with CONFIG_DEBUG_OBJECTS_RCU_HEAD=y.
*/
WARN_ON_ONCE(rcu_segcblist_empty(&rdp->cblist) != (count == 0)); WARN_ON_ONCE(rcu_segcblist_empty(&rdp->cblist) != (count == 0));
local_irq_restore(flags); local_irq_restore(flags);