Messages in this thread Patch in this message | | | Date | Wed, 12 Feb 2014 18:45:07 -0800 (PST) | From | Hugh Dickins <> | Subject | [PATCH] swapoff tmpfs radix_tree: remember to rcu_read_unlock |
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Running fsx on tmpfs with concurrent memhog-swapoff-swapon, lots of
BUG: sleeping function called from invalid context at kernel/fork.c:606 in_atomic(): 0, irqs_disabled(): 0, pid: 1394, name: swapoff 1 lock held by swapoff/1394: #0: (rcu_read_lock){.+.+.+}, at: [<ffffffff812520a1>] radix_tree_locate_item+0x1f/0x2b6 followed by ================================================ [ BUG: lock held when returning to user space! ] 3.14.0-rc1 #3 Not tainted ------------------------------------------------ swapoff/1394 is leaving the kernel with locks still held! 1 lock held by swapoff/1394: #0: (rcu_read_lock){.+.+.+}, at: [<ffffffff812520a1>] radix_tree_locate_item+0x1f/0x2b6 after which the system recovered nicely.
Whoops, I long ago forgot the rcu_read_unlock() on one unlikely branch.
Fixes: e504f3fdd63d ("tmpfs radix_tree: locate_item to speed up swapoff") Signed-off-by: Hugh Dickins <hughd@google.com> ---
Of course, the truth is that I had been hoping to break Johannes's patchset in mmotm, was thrilled to get this on that, then despondent to realize that the only bug I had found was mine. Surprised I've not seen it before in 2.5 years: tried again on 3.14-rc1, got the same after 25 minutes. Probably not serious enough for -stable, but please can we slip the fix into 3.14 - sorry, Johannes's mm-keep-page-cache-radix-tree-nodes-in-check.patch will need a refresh.
lib/radix-tree.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
--- 3.14-rc2/lib/radix-tree.c 2013-11-03 15:41:51.000000000 -0800 +++ linux/lib/radix-tree.c 2014-02-09 21:47:22.688092825 -0800 @@ -1253,8 +1253,10 @@ unsigned long radix_tree_locate_item(str node = indirect_to_ptr(node); max_index = radix_tree_maxindex(node->height); - if (cur_index > max_index) + if (cur_index > max_index) { + rcu_read_unlock(); break; + } cur_index = __locate(node, item, cur_index, &found_index); rcu_read_unlock();
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