Message ID | 20240222170749.2607485-2-sean.anderson@linux.dev (mailing list archive) |
---|---|
State | New, archived |
Headers | show |
Series | [RESEND2,net,v4,1/2] soc: fsl: qbman: Always disable interrupts when taking cgr_lock | expand |
Le 22/02/2024 à 18:07, Sean Anderson a écrit : > [Vous ne recevez pas souvent de courriers de sean.anderson@linux.dev. Découvrez pourquoi ceci est important à https://aka.ms/LearnAboutSenderIdentification ] > > 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. Why a raw spinlock to avoid problems on PREEMPT_RT, can you elaborate ? If the problem is that interrupts are already disabled, shouldn't you just change the spin_lock_irq() by spin_lock_irqsave() ? Christophe > > Fixes: 96f413f47677 ("soc/fsl/qbman: fix issue in qman_delete_cgr_safe()") > CC: stable@vger.kernel.org > 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@linux.dev> > Reviewed-by: Camelia Groza <camelia.groza@nxp.com> > Tested-by: Vladimir Oltean <vladimir.oltean@nxp.com> > > --- > > 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 >
On 2/23/24 00:38, Christophe Leroy wrote: > Le 22/02/2024 à 18:07, Sean Anderson a écrit : >> [Vous ne recevez pas souvent de courriers de sean.anderson@linux.dev. Découvrez pourquoi ceci est important à https://aka.ms/LearnAboutSenderIdentification ] >> >> 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. > > Why a raw spinlock to avoid problems on PREEMPT_RT, can you elaborate ? smp_call_function always runs its callback in hard IRQ context, even on PREEMPT_RT, where spinlocks can sleep. So we need to use raw spinlocks to ensure we aren't waiting on a sleeping task. See the first bug report for more discussion. In the longer term it would be better to switch to some other abstraction. --Sean > If the problem is that interrupts are already disabled, shouldn't you > just change the spin_lock_irq() by spin_lock_irqsave() ? > > Christophe > > >> >> Fixes: 96f413f47677 ("soc/fsl/qbman: fix issue in qman_delete_cgr_safe()") >> CC: stable@vger.kernel.org >> 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@linux.dev> >> Reviewed-by: Camelia Groza <camelia.groza@nxp.com> >> Tested-by: Vladimir Oltean <vladimir.oltean@nxp.com> >> >> --- >> >> 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 >>
Hi, On 2/23/24 11:02, Sean Anderson wrote: > On 2/23/24 00:38, Christophe Leroy wrote: >> Le 22/02/2024 à 18:07, Sean Anderson a écrit : >>> [Vous ne recevez pas souvent de courriers de sean.anderson@linux.dev. Découvrez pourquoi ceci est important à https://aka.ms/LearnAboutSenderIdentification ] >>> >>> 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. >> >> Why a raw spinlock to avoid problems on PREEMPT_RT, can you elaborate ? > > smp_call_function always runs its callback in hard IRQ context, even on > PREEMPT_RT, where spinlocks can sleep. So we need to use raw spinlocks > to ensure we aren't waiting on a sleeping task. See the first bug report > for more discussion. > > In the longer term it would be better to switch to some other > abstraction. Does this make sense to you? --Sean
Le 05/03/2024 à 19:14, Sean Anderson a écrit : > [Vous ne recevez pas souvent de courriers de sean.anderson@linux.dev. Découvrez pourquoi ceci est important à https://aka.ms/LearnAboutSenderIdentification ] > > Hi, > > On 2/23/24 11:02, Sean Anderson wrote: >> On 2/23/24 00:38, Christophe Leroy wrote: >>> Le 22/02/2024 à 18:07, Sean Anderson a écrit : >>>> [Vous ne recevez pas souvent de courriers de sean.anderson@linux.dev. Découvrez pourquoi ceci est important à https://aka.ms/LearnAboutSenderIdentification ] >>>> >>>> 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. >>> >>> Why a raw spinlock to avoid problems on PREEMPT_RT, can you elaborate ? >> >> smp_call_function always runs its callback in hard IRQ context, even on >> PREEMPT_RT, where spinlocks can sleep. So we need to use raw spinlocks >> to ensure we aren't waiting on a sleeping task. See the first bug report >> for more discussion. >> >> In the longer term it would be better to switch to some other >> abstraction. > > Does this make sense to you? Yes that fine, thanks for the clarification. Maybe you can explain that in the patch description in case you send a v5. Christophe
On 3/5/24 17:18, Christophe Leroy wrote: > > > Le 05/03/2024 à 19:14, Sean Anderson a écrit : >> [Vous ne recevez pas souvent de courriers de sean.anderson@linux.dev. Découvrez pourquoi ceci est important à https://aka.ms/LearnAboutSenderIdentification ] >> >> Hi, >> >> On 2/23/24 11:02, Sean Anderson wrote: >>> On 2/23/24 00:38, Christophe Leroy wrote: >>>> Le 22/02/2024 à 18:07, Sean Anderson a écrit : >>>>> [Vous ne recevez pas souvent de courriers de sean.anderson@linux.dev. Découvrez pourquoi ceci est important à https://aka.ms/LearnAboutSenderIdentification ] >>>>> >>>>> 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. >>>> >>>> Why a raw spinlock to avoid problems on PREEMPT_RT, can you elaborate ? >>> >>> smp_call_function always runs its callback in hard IRQ context, even on >>> PREEMPT_RT, where spinlocks can sleep. So we need to use raw spinlocks >>> to ensure we aren't waiting on a sleeping task. See the first bug report >>> for more discussion. >>> >>> In the longer term it would be better to switch to some other >>> abstraction. >> >> Does this make sense to you? > > Yes that fine, thanks for the clarification. Maybe you can explain that > in the patch description in case you send a v5. Hm, I thought I put this description in the commit message already. Maybe something like | 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. would be clearer. --Sean
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; }