| Message ID | 1519780965-15292-1-git-send-email-greearb@candelatech.com (mailing list archive) |
|---|---|
| State | RFC |
| Delegated to: | Kalle Valo |
| Headers | show |
On 28 February 2018 at 02:22, <greearb@candelatech.com> wrote: [...] > @@ -2086,8 +2087,28 @@ static void ath10k_pci_hif_stop(struct ath10k *ar) > ath10k_pci_irq_disable(ar); > ath10k_pci_irq_sync(ar); > ath10k_pci_flush(ar); > - napi_synchronize(&ar->napi); > - napi_disable(&ar->napi); > + > + /* Calling napi_disable twice in a row (w/out starting it and/or without > + * having NAPI active leads to deadlock because napi_disable sets > + * NAPI_STATE_SCHED and NAPI_STATE_NPSVC when it returns, as far as I > + * can tell. So, guard this call to napi_disable. I believe the > + * failure case is something like this: > + * rmmod ath10k_pci ath10k_core > + * Firmware crashes before hif_stop is called by the rmmod path > + * The crash handling logic calls hif_stop > + * Then rmmod gets around to calling hif_stop, but spins endlessly > + * in napi_synchronize. > + * > + * I think one way this could happen is that ath10k_stop checks > + * for state != ATH10K_STATE_OFF, but STATE_RESTARTING is also > + * a possibility. That might be how we can have hif_stop called twice > + * without a hif_start in between. --Ben > + */ > + if (ar->napi_enabled) { > + napi_synchronize(&ar->napi); > + napi_disable(&ar->napi); > + ar->napi_enabled = false; > + } Looking at the code and your comment the described fail case seems legit. I would consider tuning ath10k_stop() so that it calls ath10k_halt() only if ar->state != OFF & ar->state != RESTARTING though. Or did you try already? While your approach will probably work it won't prevent other non-NAPI bad things from happening. Even if there's nothing today it might creep up in the future. And you'd need to update ahb.c too. Michał
On 02/28/2018 09:31 AM, Michał Kazior wrote: > On 28 February 2018 at 02:22, <greearb@candelatech.com> wrote: > [...] >> @@ -2086,8 +2087,28 @@ static void ath10k_pci_hif_stop(struct ath10k *ar) >> ath10k_pci_irq_disable(ar); >> ath10k_pci_irq_sync(ar); >> ath10k_pci_flush(ar); >> - napi_synchronize(&ar->napi); >> - napi_disable(&ar->napi); >> + >> + /* Calling napi_disable twice in a row (w/out starting it and/or without >> + * having NAPI active leads to deadlock because napi_disable sets >> + * NAPI_STATE_SCHED and NAPI_STATE_NPSVC when it returns, as far as I >> + * can tell. So, guard this call to napi_disable. I believe the >> + * failure case is something like this: >> + * rmmod ath10k_pci ath10k_core >> + * Firmware crashes before hif_stop is called by the rmmod path >> + * The crash handling logic calls hif_stop >> + * Then rmmod gets around to calling hif_stop, but spins endlessly >> + * in napi_synchronize. >> + * >> + * I think one way this could happen is that ath10k_stop checks >> + * for state != ATH10K_STATE_OFF, but STATE_RESTARTING is also >> + * a possibility. That might be how we can have hif_stop called twice >> + * without a hif_start in between. --Ben >> + */ >> + if (ar->napi_enabled) { >> + napi_synchronize(&ar->napi); >> + napi_disable(&ar->napi); >> + ar->napi_enabled = false; >> + } > > Looking at the code and your comment the described fail case seems > legit. I would consider tuning ath10k_stop() so that it calls > ath10k_halt() only if ar->state != OFF & ar->state != RESTARTING > though. Or did you try already? I did not try tuning ath10k_stop(). The code in this area is quite complex, and in my opinion trying to keep the start/stop calls exactly matched without individual 'has_started' flags seems ripe for bugs. > While your approach will probably work it won't prevent other non-NAPI > bad things from happening. Even if there's nothing today it might > creep up in the future. And you'd need to update ahb.c too. I'll update ahb.c to match. Thanks, Ben > > > Michał >
diff --git a/drivers/net/wireless/ath/ath10k/core.h b/drivers/net/wireless/ath/ath10k/core.h index 72b4495..c7ba49f 100644 --- a/drivers/net/wireless/ath/ath10k/core.h +++ b/drivers/net/wireless/ath/ath10k/core.h @@ -1205,6 +1205,7 @@ struct ath10k { /* NAPI */ struct net_device napi_dev; struct napi_struct napi; + bool napi_enabled; struct work_struct stop_scan_work; diff --git a/drivers/net/wireless/ath/ath10k/pci.c b/drivers/net/wireless/ath/ath10k/pci.c index 398e413..9131e15 100644 --- a/drivers/net/wireless/ath/ath10k/pci.c +++ b/drivers/net/wireless/ath/ath10k/pci.c @@ -1956,6 +1956,7 @@ static int ath10k_pci_hif_start(struct ath10k *ar) ath10k_dbg(ar, ATH10K_DBG_BOOT, "boot hif start\n"); napi_enable(&ar->napi); + ar->napi_enabled = true; ath10k_pci_irq_enable(ar); ath10k_pci_rx_post(ar); @@ -2086,8 +2087,28 @@ static void ath10k_pci_hif_stop(struct ath10k *ar) ath10k_pci_irq_disable(ar); ath10k_pci_irq_sync(ar); ath10k_pci_flush(ar); - napi_synchronize(&ar->napi); - napi_disable(&ar->napi); + + /* Calling napi_disable twice in a row (w/out starting it and/or without + * having NAPI active leads to deadlock because napi_disable sets + * NAPI_STATE_SCHED and NAPI_STATE_NPSVC when it returns, as far as I + * can tell. So, guard this call to napi_disable. I believe the + * failure case is something like this: + * rmmod ath10k_pci ath10k_core + * Firmware crashes before hif_stop is called by the rmmod path + * The crash handling logic calls hif_stop + * Then rmmod gets around to calling hif_stop, but spins endlessly + * in napi_synchronize. + * + * I think one way this could happen is that ath10k_stop checks + * for state != ATH10K_STATE_OFF, but STATE_RESTARTING is also + * a possibility. That might be how we can have hif_stop called twice + * without a hif_start in between. --Ben + */ + if (ar->napi_enabled) { + napi_synchronize(&ar->napi); + napi_disable(&ar->napi); + ar->napi_enabled = false; + } spin_lock_irqsave(&ar_pci->ps_lock, flags); WARN_ON(ar_pci->ps_wake_refcount > 0);