Re: 2.6.35-rc2-git1 - lib/idr.c:605 invokedrcu_dereference_check() without protection!
From: Paul E. McKenney
Date: Mon Jun 07 2010 - 20:14:02 EST
On Mon, Jun 07, 2010 at 02:23:17PM -0400, Miles Lane wrote:
> [ 2.677955] [ INFO: suspicious rcu_dereference_check() usage. ]
> [ 2.679089] ---------------------------------------------------
> [ 2.680276] lib/idr.c:605 invoked rcu_dereference_check() without protection!
> [ 2.681499]
> [ 2.681500] other info that might help us debug this:
> [ 2.681501]
> [ 2.685509]
> [ 2.685510] rcu_scheduler_active = 1, debug_locks = 1
> [ 2.688221] 1 lock held by swapper/1:
> [ 2.689587] #0: (mtd_table_mutex){+.+...}, at:
> [<ffffffff812bea45>] register_mtd_user+0x1a/0x69
> [ 2.691096]
> [ 2.691098] stack backtrace:
> [ 2.694059] Pid: 1, comm: swapper Not tainted 2.6.35-rc2-git1 #8
> [ 2.695601] Call Trace:
> [ 2.697243] [<ffffffff81064e9c>] lockdep_rcu_dereference+0x9d/0xa5
> [ 2.698868] [<ffffffff811b9c86>] idr_get_next+0x60/0x124
> [ 2.700556] [<ffffffff812be779>] __mtd_next_device+0x1b/0x1d
> [ 2.702238] [<ffffffff812bea7c>] register_mtd_user+0x51/0x69
> [ 2.703964] [<ffffffff816cca45>] init_mtdchar+0xb3/0xd3
> [ 2.705686] [<ffffffff816cc992>] ? init_mtdchar+0x0/0xd3
> [ 2.707470] [<ffffffff810001ef>] do_one_initcall+0x59/0x14e
> [ 2.709255] [<ffffffff816a768a>] kernel_init+0x144/0x1ce
> [ 2.711082] [<ffffffff81003054>] kernel_thread_helper+0x4/0x10
> [ 2.712862] [<ffffffff813ca480>] ? restore_args+0x0/0x30
> [ 2.714647] [<ffffffff816a7546>] ? kernel_init+0x0/0x1ce
> [ 2.716415] [<ffffffff81003050>] ? kernel_thread_helper+0x0/0x10
This looks like a new one! Does the following patch take care of it?
Thanx, Paul
------------------------------------------------------------------------
commit 2d54a6c31b72c902b09d365e9c66205a5c07e549
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Date: Mon Jun 7 17:09:45 2010 -0700
idr: fix RCU lockdep splat in idr_get_next()
Convert to rcu_dereference_raw() given that many callers may have many
different locking models.
Located-by: Miles Lane <miles.lane@xxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
diff --git a/lib/idr.c b/lib/idr.c
index 2eb1dca..f099f25 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -599,7 +599,7 @@ void *idr_get_next(struct idr *idp, int *nextidp)
/* find first ent */
n = idp->layers * IDR_BITS;
max = 1 << n;
- p = rcu_dereference(idp->top);
+ p = rcu_dereference_raw(idp->top);
if (!p)
return NULL;
@@ -607,7 +607,7 @@ void *idr_get_next(struct idr *idp, int *nextidp)
while (n > 0 && p) {
n -= IDR_BITS;
*paa++ = p;
- p = rcu_dereference(p->ary[(id >> n) & IDR_MASK]);
+ p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]);
}
if (p) {
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/