On 1/8/24 11:19, Sean Anderson wrote:

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()") Reported-by: Vladimir Oltean vladimir.oltean@nxp.com Closes: https://lore.kernel.org/all/20230323153935.nofnjucqjqnz34ej@skbuf/ Reported-by: Steffen Trumtrar s.trumtrar@pengutronix.de Closes: https://lore.kernel.org/linux-arm-kernel/87wmsyvclu.fsf@pengutronix.de/ Signed-off-by: Sean Anderson sean.anderson@seco.com Reviewed-by: Camelia Groza camelia.groza@nxp.com Tested-by: Vladimir Oltean vladimir.oltean@nxp.com

---

Please backport these fixes when applied. This bug has been reported multiple times (see links above).

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;

}

ping

I'd like to get this in for 6.8.

Would it be more convenient for this to go via net?

--Sean