From: Filipe Manana <[email protected]>
Teach _check_dmesg to look for improper RCU usage and circular locking
dependency messages. It's useful to check for these as they might point
to a real problem in the filesystem's implementation (or the current
implementation just confuses the checker, probably worth simplifying
the filesystem's implementation).
Currently the test btrfs/071 for example triggers such warnings:
[ 912.924839] ===============================
[ 912.925617] [ INFO: suspicious RCU usage. ]
[ 912.926394] 4.3.0-rc5-btrfs-next-17+ #1 Not tainted
[ 912.927274] -------------------------------
[ 912.928364] fs/btrfs/volumes.c:1977 suspicious rcu_dereference_check() usage!
[ 912.929626]
[ 912.929626] other info that might help us debug this:
[ 912.929626]
[ 912.931197]
[ 912.931197] rcu_scheduler_active = 1, debug_locks = 1
[ 912.933822] 4 locks held by btrfs/6400:
[ 912.934558] #0:
(&fs_info->dev_replace.lock_finishing_cancel_unmount){+.+...}, at:
[<ffffffffa046a193>] btrfs_dev_replace_finishing+0x3e/0x696 [btrfs]
[ 912.948929] #1: (uuid_mutex){+.+.+.}, at: [<ffffffffa046a24a>]
btrfs_dev_replace_finishing+0xf5/0x696 [btrfs]
[ 912.950987] #2: (&fs_devs->device_list_mutex){+.+.+.}, at:
[<ffffffffa046a263>] btrfs_dev_replace_finishing+0x10e/0x696 [btrfs]
[ 912.953265] #3: (&fs_info->chunk_mutex){+.+...}, at: [<ffffffffa046a278>]
btrfs_dev_replace_finishing+0x123/0x696 [btrfs]
(...)
[ 912.987973] ======================================================
[ 912.989242] [ INFO: possible circular locking dependency detected ]
[ 912.990583] 4.3.0-rc5-btrfs-next-17+ #1 Not tainted
[ 912.990801] -------------------------------------------------------
[ 912.990801] btrfs/6400 is trying to acquire lock:
[ 912.990801] (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8119d202>]
__blkdev_get+0xa3/0x3d9
[ 912.990801]
[ 912.990801] but task is already holding lock:
[ 912.990801] (&fs_info->chunk_mutex){+.+.+.}, at: [<ffffffffa046a278>]
btrfs_dev_replace_finishing+0x123/0x696 [btrfs]
[ 912.990801]
[ 912.990801] which lock already depends on the new lock.
[ 912.990801]
[ 912.990801]
[ 912.990801] the existing dependency chain (in reverse order) is:
(...)
Signed-off-by: Filipe Manana <[email protected]>
---
common/rc | 2 ++
1 file changed, 2 insertions(+)
diff --git a/common/rc b/common/rc
index 4c2f42c..dd50aa9 100644
--- a/common/rc
+++ b/common/rc
@@ -3055,6 +3055,8 @@ _check_dmesg()
-e "Oops:" \
-e "possible recursive locking detected" \
-e "Internal error" \
+ -e "INFO: suspicious RCU usage" \
+ -e "INFO: possible circular locking dependency detected" \
$seqres.dmesg
if [ $? -eq 0 ]; then
echo "_check_dmesg: something found in dmesg (see
$seqres.dmesg)"
--
2.1.3
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