4.4-stable review patch. If anyone has any objections, please let me know.
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From: Bart Van Assche bart.vanassche@wdc.com
[ Upstream commit 624fa7790f80575a4ec28fbdb2034097dc18d051 ]
In the scsi_transport_srp implementation it cannot be avoided to iterate over a klist from atomic context when using the legacy block layer instead of blk-mq. Hence this patch that makes it safe to use klists in atomic context. This patch avoids that lockdep reports the following:
WARNING: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected Possible interrupt unsafe locking scenario:
CPU0 CPU1 ---- ---- lock(&(&k->k_lock)->rlock); local_irq_disable(); lock(&(&q->__queue_lock)->rlock); lock(&(&k->k_lock)->rlock); <Interrupt> lock(&(&q->__queue_lock)->rlock);
stack backtrace: Workqueue: kblockd blk_timeout_work Call Trace: dump_stack+0xa4/0xf5 check_usage+0x6e6/0x700 __lock_acquire+0x185d/0x1b50 lock_acquire+0xd2/0x260 _raw_spin_lock+0x32/0x50 klist_next+0x47/0x190 device_for_each_child+0x8e/0x100 srp_timed_out+0xaf/0x1d0 [scsi_transport_srp] scsi_times_out+0xd4/0x410 [scsi_mod] blk_rq_timed_out+0x36/0x70 blk_timeout_work+0x1b5/0x220 process_one_work+0x4fe/0xad0 worker_thread+0x63/0x5a0 kthread+0x1c1/0x1e0 ret_from_fork+0x24/0x30
See also commit c9ddf73476ff ("scsi: scsi_transport_srp: Fix shost to rport translation").
Signed-off-by: Bart Van Assche bart.vanassche@wdc.com Cc: Martin K. Petersen martin.petersen@oracle.com Cc: James Bottomley jejb@linux.vnet.ibm.com Acked-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Martin K. Petersen martin.petersen@oracle.com Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- lib/klist.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)
--- a/lib/klist.c +++ b/lib/klist.c @@ -336,8 +336,9 @@ struct klist_node *klist_prev(struct kli void (*put)(struct klist_node *) = i->i_klist->put; struct klist_node *last = i->i_cur; struct klist_node *prev; + unsigned long flags;
- spin_lock(&i->i_klist->k_lock); + spin_lock_irqsave(&i->i_klist->k_lock, flags);
if (last) { prev = to_klist_node(last->n_node.prev); @@ -356,7 +357,7 @@ struct klist_node *klist_prev(struct kli prev = to_klist_node(prev->n_node.prev); }
- spin_unlock(&i->i_klist->k_lock); + spin_unlock_irqrestore(&i->i_klist->k_lock, flags);
if (put && last) put(last); @@ -377,8 +378,9 @@ struct klist_node *klist_next(struct kli void (*put)(struct klist_node *) = i->i_klist->put; struct klist_node *last = i->i_cur; struct klist_node *next; + unsigned long flags;
- spin_lock(&i->i_klist->k_lock); + spin_lock_irqsave(&i->i_klist->k_lock, flags);
if (last) { next = to_klist_node(last->n_node.next); @@ -397,7 +399,7 @@ struct klist_node *klist_next(struct kli next = to_klist_node(next->n_node.next); }
- spin_unlock(&i->i_klist->k_lock); + spin_unlock_irqrestore(&i->i_klist->k_lock, flags);
if (put && last) put(last);