Running xfstests 273 in a loop reproduces an XFS lockup due to
xfsaild entering idle mode indefinitely. The following
high-level sequence of events leads to the hang:
- xfsaild is running with a cached target lsn
- xfs_ail_push() is invoked, updates ailp->xa_target_lsn and
invokes wake_up_process(). wake_up_process() returns 0
because xfsaild is already running.
- xfsaild enters idle mode having met its current target.
Once in the described state, xfs_ail_push() is invoked many
more times with the already set threshold_lsn, but these calls
do not lead to wake_up_process() calls because no further
invocations result in moving the threshold_lsn forward. Add a
flag to xfs_ail to capture whether an issued wake actually
succeeds. If not, continue issuing wakes until we know one has
been successful for the current target.
Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx>
---
fs/xfs/xfs_trans_ail.c | 4 ++--
fs/xfs/xfs_trans_priv.h | 1 +
2 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/fs/xfs/xfs_trans_ail.c b/fs/xfs/xfs_trans_ail.c
index 8a122d3..8b49be8 100644
--- a/fs/xfs/xfs_trans_ail.c
+++ b/fs/xfs/xfs_trans_ail.c
@@ -564,7 +564,7 @@ xfs_ail_push(
lip = xfs_ail_min(ailp);
if (!lip || XFS_FORCED_SHUTDOWN(ailp->xa_mount) ||
- XFS_LSN_CMP(threshold_lsn, ailp->xa_target) <= 0)
+ ((XFS_LSN_CMP(threshold_lsn, ailp->xa_target) <= 0) && !ailp->xa_pending_wake))
return;
/*
@@ -575,7 +575,7 @@ xfs_ail_push(
xfs_trans_ail_copy_lsn(ailp, &ailp->xa_target, &threshold_lsn);
smp_wmb();
- wake_up_process(ailp->xa_task);
+ ailp->xa_pending_wake = !wake_up_process(ailp->xa_task);
}
/*
diff --git a/fs/xfs/xfs_trans_priv.h b/fs/xfs/xfs_trans_priv.h
index fb62377..688ef73 100644
--- a/fs/xfs/xfs_trans_priv.h
+++ b/fs/xfs/xfs_trans_priv.h
@@ -71,6 +71,7 @@ struct xfs_ail {
spinlock_t xa_lock;
xfs_lsn_t xa_last_pushed_lsn;
int xa_log_flush;
+ int xa_pending_wake;
struct list_head xa_buf_list;
wait_queue_head_t xa_empty;
};
--
1.7.7.6
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