[PATCH net v5 2/2] soc: fsl: qbman: Use raw spinlock for cgr_lock

[Sean Anderson]

smp_call_function always runs its callback in hard IRQ context, even on
PREEMPT_RT, where spinlocks can sleep. So we need to use a raw spinlock
for cgr_lock to ensure we aren't waiting on a sleeping task.

Although this bug has existed for a while, it was not apparent until
commit ef2a8d5478b9 ("net: dpaa: Adjust queue depth on rate change")
which invokes smp_call_function_single via qman_update_cgr_safe every
time a link goes up or down.

Fixes: 96f413f47677 ("soc/fsl/qbman: fix issue in qman_delete_cgr_safe()")
CC: stable at vger.kernel.org
Reported-by: Vladimir Oltean <vladimir.oltean at nxp.com>
Closes: https://lore.kernel.org/all/20230323153935.nofnjucqjqnz34ej@skbuf/
Reported-by: Steffen Trumtrar <s.trumtrar at pengutronix.de>
Closes: https://lore.kernel.org/linux-arm-kernel/87wmsyvclu.fsf@pengutronix.de/
Signed-off-by: Sean Anderson <sean.anderson at linux.dev>
Reviewed-by: Camelia Groza <camelia.groza at nxp.com>
Tested-by: Vladimir Oltean <vladimir.oltean at nxp.com>

---

Changes in v5:
- Clarify commit message

Changes in v4:
- Add a note about how raw spinlocks aren't quite right

Changes in v3:
- Change blamed commit to something more appropriate

 drivers/soc/fsl/qbman/qman.c | 25 ++++++++++++++-----------
 1 file changed, 14 insertions(+), 11 deletions(-)

diff --git a/drivers/soc/fsl/qbman/qman.c b/drivers/soc/fsl/qbman/qman.c
index 1bf1f1ea67f0..7e9074519ad2 100644
--- a/drivers/soc/fsl/qbman/qman.c
+++ b/drivers/soc/fsl/qbman/qman.c
@@ -991,7 +991,7 @@ struct qman_portal {
 	/* linked-list of CSCN handlers. */
 	struct list_head cgr_cbs;
 	/* list lock */
-	spinlock_t cgr_lock;
+	raw_spinlock_t cgr_lock;
 	struct work_struct congestion_work;
 	struct work_struct mr_work;
 	char irqname[MAX_IRQNAME];
@@ -1281,7 +1281,7 @@ static int qman_create_portal(struct qman_portal *portal,
 		/* if the given mask is NULL, assume all CGRs can be seen */
 		qman_cgrs_fill(&portal->cgrs[0]);
 	INIT_LIST_HEAD(&portal->cgr_cbs);
-	spin_lock_init(&portal->cgr_lock);
+	raw_spin_lock_init(&portal->cgr_lock);
 	INIT_WORK(&portal->congestion_work, qm_congestion_task);
 	INIT_WORK(&portal->mr_work, qm_mr_process_task);
 	portal->bits = 0;
@@ -1456,11 +1456,14 @@ static void qm_congestion_task(struct work_struct *work)
 	union qm_mc_result *mcr;
 	struct qman_cgr *cgr;
 
-	spin_lock_irq(&p->cgr_lock);
+	/*
+	 * FIXME: QM_MCR_TIMEOUT is 10ms, which is too long for a raw spinlock!
+	 */
+	raw_spin_lock_irq(&p->cgr_lock);
 	qm_mc_start(&p->p);
 	qm_mc_commit(&p->p, QM_MCC_VERB_QUERYCONGESTION);
 	if (!qm_mc_result_timeout(&p->p, &mcr)) {
-		spin_unlock_irq(&p->cgr_lock);
+		raw_spin_unlock_irq(&p->cgr_lock);
 		dev_crit(p->config->dev, "QUERYCONGESTION timeout\n");
 		qman_p_irqsource_add(p, QM_PIRQ_CSCI);
 		return;
@@ -1476,7 +1479,7 @@ static void qm_congestion_task(struct work_struct *work)
 	list_for_each_entry(cgr, &p->cgr_cbs, node)
 		if (cgr->cb && qman_cgrs_get(&c, cgr->cgrid))
 			cgr->cb(p, cgr, qman_cgrs_get(&rr, cgr->cgrid));
-	spin_unlock_irq(&p->cgr_lock);
+	raw_spin_unlock_irq(&p->cgr_lock);
 	qman_p_irqsource_add(p, QM_PIRQ_CSCI);
 }
 
@@ -2440,7 +2443,7 @@ int qman_create_cgr(struct qman_cgr *cgr, u32 flags,
 	preempt_enable();
 
 	cgr->chan = p->config->channel;
-	spin_lock_irq(&p->cgr_lock);
+	raw_spin_lock_irq(&p->cgr_lock);
 
 	if (opts) {
 		struct qm_mcc_initcgr local_opts = *opts;
@@ -2477,7 +2480,7 @@ int qman_create_cgr(struct qman_cgr *cgr, u32 flags,
 	    qman_cgrs_get(&p->cgrs[1], cgr->cgrid))
 		cgr->cb(p, cgr, 1);
 out:
-	spin_unlock_irq(&p->cgr_lock);
+	raw_spin_unlock_irq(&p->cgr_lock);
 	put_affine_portal();
 	return ret;
 }
@@ -2512,7 +2515,7 @@ int qman_delete_cgr(struct qman_cgr *cgr)
 		return -EINVAL;
 
 	memset(&local_opts, 0, sizeof(struct qm_mcc_initcgr));
-	spin_lock_irqsave(&p->cgr_lock, irqflags);
+	raw_spin_lock_irqsave(&p->cgr_lock, irqflags);
 	list_del(&cgr->node);
 	/*
 	 * If there are no other CGR objects for this CGRID in the list,
@@ -2537,7 +2540,7 @@ int qman_delete_cgr(struct qman_cgr *cgr)
 		/* add back to the list */
 		list_add(&cgr->node, &p->cgr_cbs);
 release_lock:
-	spin_unlock_irqrestore(&p->cgr_lock, irqflags);
+	raw_spin_unlock_irqrestore(&p->cgr_lock, irqflags);
 	put_affine_portal();
 	return ret;
 }
@@ -2577,9 +2580,9 @@ static int qman_update_cgr(struct qman_cgr *cgr, struct qm_mcc_initcgr *opts)
 	if (!p)
 		return -EINVAL;
 
-	spin_lock_irqsave(&p->cgr_lock, irqflags);
+	raw_spin_lock_irqsave(&p->cgr_lock, irqflags);
 	ret = qm_modify_cgr(cgr, 0, opts);
-	spin_unlock_irqrestore(&p->cgr_lock, irqflags);
+	raw_spin_unlock_irqrestore(&p->cgr_lock, irqflags);
 	put_affine_portal();
 	return ret;
 }
-- 
2.35.1.1320.gc452695387.dirty