[RESEND,net,v4,2/2] soc: fsl: qbman: Use raw spinlock for cgr_lock

Commit Message

Sean Anderson Feb. 15, 2024, 4:23 p.m. UTC

cgr_lock may be locked with interrupts already disabled by
smp_call_function_single. As such, we must use a raw spinlock to avoid
problems on PREEMPT_RT kernels. 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: [e-mail]
Reported-by: Vladimir Oltean <[e-mail]>
Closes: https://lore.kernel.org/all/20230323153935.nofnjucqjqnz34ej@skbuf/
Reported-by: Steffen Trumtrar <[e-mail]>
Closes: https://lore.kernel.org/linux-arm-kernel/[e-mail]/
Signed-off-by: Sean Anderson <[e-mail]>
Reviewed-by: Camelia Groza <[e-mail]>
Tested-by: Vladimir Oltean <[e-mail]>

---

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(-)

--
2.35.1.1320.gc452695387.dirty


[Embedded World 2024, SECO SpA]<https://www.messe-ticket.de/Nuernberg/embeddedworld2024/Register/ew24517689>

Patch

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;
 }