[patch 4/4] vunmap: Fix racy use of rcu_head
From: Mathieu Desnoyers
Date: Tue Oct 06 2009 - 10:42:54 EST
Repetitive use of vmap/vunmap on the same address triggers this bug.
Simplest fix: directly kfree the data structure rather than doing it lazily.
Impact:
(-) slight slowdown on vunmap
(+) stop messing up rcu callback lists ;)
Caught it with DEBUG_RCU_HEAD, running LTTng armall/disarmall in loops.
Immediate values (with breakpoint-ipi scheme) are still using vunmap.
------------[ cut here ]------------
WARNING: at kernel/rcutree.c:1199 __call_rcu+0x181/0x190()
Hardware name: X7DAL
Modules linked in: loop ltt_statedump ltt_userspace_event ipc_tr]
Pid: 4527, comm: ltt-armall Not tainted 2.6.30.9-trace #30
Call Trace:
[<ffffffff8027b181>] ? __call_rcu+0x181/0x190
[<ffffffff8027b181>] ? __call_rcu+0x181/0x190
[<ffffffff8023a6a9>] ? warn_slowpath_common+0x79/0xd0
[<ffffffff802b4890>] ? rcu_free_va+0x0/0x10
[<ffffffff8027b181>] ? __call_rcu+0x181/0x190
[<ffffffff802b5298>] ? __purge_vmap_area_lazy+0x1a8/0x1e0
[<ffffffff802b59d4>] ? free_unmap_vmap_area_noflush+0x74/0x80
[<ffffffff802b5a0e>] ? remove_vm_area+0x2e/0x80
[<ffffffff802b5b35>] ? __vunmap+0x45/0xf0
[<ffffffffa002e826>] ? ltt_statedump_start+0x7b6/0x820 [ltt_sta]
[<ffffffff8068978a>] ? arch_imv_update+0x16a/0x2f0
[<ffffffff8027dd13>] ? imv_update_range+0x53/0xa0
[<ffffffff8026235b>] ? _module_imv_update+0x4b/0x60
[<ffffffff80262385>] ? module_imv_update+0x15/0x30
[<ffffffff80280049>] ? marker_probe_register+0x149/0xb90
[<ffffffff8040c8e0>] ? ltt_vtrace+0x0/0x8c0
[<ffffffff80409330>] ? ltt_marker_connect+0xd0/0x150
[<ffffffff8040f8dc>] ? marker_enable_write+0xec/0x120
[<ffffffff802c6cb8>] ? __dentry_open+0x268/0x350
[<ffffffff80280b2c>] ? marker_probe_cb+0x9c/0x170
[<ffffffff80280b2c>] ? marker_probe_cb+0x9c/0x170
[<ffffffff802c973b>] ? vfs_write+0xcb/0x170
[<ffffffff802c9984>] ? sys_write+0x64/0x130
[<ffffffff8020beeb>] ? system_call_fastpath+0x16/0x1b
---[ end trace ef92443e716fa199 ]---
------------[ cut here ]------------
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxx>
CC: cl@xxxxxxxxxxxxxxxxxxxx
CC: mingo@xxxxxxx
CC: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
CC: linux-mm@xxxxxxxxx
CC: akpm@xxxxxxxxxxxxxxxxxxxx
---
mm/vmalloc.c | 18 ++----------------
1 file changed, 2 insertions(+), 16 deletions(-)
Index: linux-2.6-lttng/mm/vmalloc.c
===================================================================
--- linux-2.6-lttng.orig/mm/vmalloc.c 2009-10-06 09:37:04.000000000 -0400
+++ linux-2.6-lttng/mm/vmalloc.c 2009-10-06 09:37:56.000000000 -0400
@@ -417,13 +417,6 @@ overflow:
return va;
}
-static void rcu_free_va(struct rcu_head *head)
-{
- struct vmap_area *va = container_of(head, struct vmap_area, rcu_head);
-
- kfree(va);
-}
-
static void __free_vmap_area(struct vmap_area *va)
{
BUG_ON(RB_EMPTY_NODE(&va->rb_node));
@@ -431,7 +424,7 @@ static void __free_vmap_area(struct vmap
RB_CLEAR_NODE(&va->rb_node);
list_del_rcu(&va->list);
- call_rcu(&va->rcu_head, rcu_free_va);
+ kfree(va);
}
/*
@@ -757,13 +750,6 @@ static struct vmap_block *new_vmap_block
return vb;
}
-static void rcu_free_vb(struct rcu_head *head)
-{
- struct vmap_block *vb = container_of(head, struct vmap_block, rcu_head);
-
- kfree(vb);
-}
-
static void free_vmap_block(struct vmap_block *vb)
{
struct vmap_block *tmp;
@@ -778,7 +764,7 @@ static void free_vmap_block(struct vmap_
BUG_ON(tmp != vb);
free_unmap_vmap_area_noflush(vb->va);
- call_rcu(&vb->rcu_head, rcu_free_vb);
+ kfree(vb);
}
static void *vb_alloc(unsigned long size, gfp_t gfp_mask)
--
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
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