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[SCSI] libfc: fix a circular locking warning during sending RRQ 

Currently the fc_exch_rrq is called with fc_exch's ex_lock held.
The fc_exch_rrq allocates new exch and that requires taking
ex_lock again after EM lock. This locking order causes warning,
see more details on this warning at :-

 http://www.open-fcoe.org/pipermail/devel/2009-July/003251.html

This patch fixes this by dropping the ex_lock before calling
fc_exch_rrq().

The fc_exch_rrq needs to grab ex_lock lock again to schedule
RRQ retry and in the meanwhile fc_exch_reset could occur before
ex_lock is grabbed inside fc_exch_rrq. So to handle this case,
this patch adds additional check to detect fc_exch_reset after
ex_lock acquired and in case the fc_exch_reset occurred then
abandons the RRQ retry and releases the exch.

Signed-off-by: Vasu Dev <vasu.dev@intel.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
This commit is contained in:
Vasu Dev 2009-07-28 17:33:37 -07:00 committed by James Bottomley
parent 16ed55f9de
commit a0cc1ecc09
1 changed files with 15 additions and 8 deletions
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23
drivers/scsi/libfc/fc_exch.c
View File

@ -415,9 +415,9 @@ static void fc_exch_timeout(struct work_struct *work)
e_stat = ep->esb_stat;
if (e_stat & ESB_ST_COMPLETE) {
ep->esb_stat = e_stat & ~ESB_ST_REC_QUAL;
spin_unlock_bh(&ep->ex_lock);
if (e_stat & ESB_ST_REC_QUAL)
fc_exch_rrq(ep);
spin_unlock_bh(&ep->ex_lock);
goto done;
} else {
resp = ep->resp;
@ -1624,14 +1624,14 @@ static void fc_exch_rrq(struct fc_exch *ep)
struct fc_lport *lp;
struct fc_els_rrq *rrq;
struct fc_frame *fp;
struct fc_seq *rrq_sp;
u32 did;
lp = ep->lp;
fp = fc_frame_alloc(lp, sizeof(*rrq));
if (!fp)
return;
goto retry;
rrq = fc_frame_payload_get(fp, sizeof(*rrq));
memset(rrq, 0, sizeof(*rrq));
rrq->rrq_cmd = ELS_RRQ;
@ -1647,13 +1647,20 @@ static void fc_exch_rrq(struct fc_exch *ep)
fc_host_port_id(lp->host), FC_TYPE_ELS,
FC_FC_FIRST_SEQ | FC_FC_END_SEQ | FC_FC_SEQ_INIT, 0);
rrq_sp = fc_exch_seq_send(lp, fp, fc_exch_rrq_resp, NULL, ep,
lp->e_d_tov);
if (!rrq_sp) {
ep->esb_stat |= ESB_ST_REC_QUAL;
fc_exch_timer_set_locked(ep, ep->r_a_tov);
if (fc_exch_seq_send(lp, fp, fc_exch_rrq_resp, NULL, ep, lp->e_d_tov))
return;
retry:
spin_lock_bh(&ep->ex_lock);
if (ep->state & (FC_EX_RST_CLEANUP | FC_EX_DONE)) {
spin_unlock_bh(&ep->ex_lock);
/* drop hold for rec qual */
fc_exch_release(ep);
return;
}
ep->esb_stat |= ESB_ST_REC_QUAL;
fc_exch_timer_set_locked(ep, ep->r_a_tov);
spin_unlock_bh(&ep->ex_lock);
}