| Message ID | 20241031212632.2799127-1-bvanassche@acm.org |
|---|---|
| State | New |
| Headers | show |
| Series | scsi: ufs: Start the RTC update work later | expand |
On 11/1/24 12:53 AM, Manivannan Sadhasivam wrote: > On Thu, Oct 31, 2024 at 02:26:24PM -0700, Bart Van Assche wrote: >> The RTC update work involves runtime resuming the UFS controller. Hence, >> only start the RTC update work after runtime power management in the UFS >> driver has been fully initialized. This patch fixes the following kernel >> crash: >> >> Internal error: Oops: 0000000096000006 [#1] PREEMPT SMP >> Workqueue: events ufshcd_rtc_work >> Call trace: >> _raw_spin_lock_irqsave+0x34/0x8c (P) >> pm_runtime_get_if_active+0x24/0x9c (L) >> pm_runtime_get_if_active+0x24/0x9c >> ufshcd_rtc_work+0x138/0x1b4 >> process_one_work+0x148/0x288 >> worker_thread+0x2cc/0x3d4 >> kthread+0x110/0x114 >> ret_from_fork+0x10/0x20 >> >> Reported-by: Neil Armstrong <neil.armstrong@linaro.org> >> Closes: https://lore.kernel.org/linux-scsi/0c0bc528-fdc2-4106-bc99-f23ae377f6f5@linaro.org/ >> Fixes: 6bf999e0eb41 ("scsi: ufs: core: Add UFS RTC support") >> Cc: Bean Huo <beanhuo@micron.com> >> Cc: stable@vger.kernel.org >> Signed-off-by: Bart Van Assche <bvanassche@acm.org> > > Bart, Thanks for the fix! While looking into this patch, I also found the > weirdness of the ufshcd_rpm_*() helpers in ufshcd-priv.h. Their naming doesn't > seem to indicate whether those helpers are for WLUN or for HBA. Also, I don't > see the benefit of these helpers since they just wrap generic pm_runtime* > calls. Then there are other open coding instances in the ufshcd.c. Like > > pm_runtime_suspended(&hba->ufs_device_wlun->sdev_gendev) > pm_runtime_set_active(&hba->ufs_device_wlun->sdev_gendev) > > Moreover, we do check for the presence of hba->ufs_device_wlun before calling > ufshcd_rpm_get_sync() in ufshcd_remove(). This could be one other way to fix > this null ptr dereference even though I wouldn't recommend doing so as calling > rtc_work early is pointless. > > So I think we should remove these helpers to avoid having these discrepancies. > WDYT? Hi Manivannan, In the context of the Linux kernel, in general, one-line helper functions are considered questionable. In this case I prefer to keep the helper functions since these encapsulate an implementation detail, namely that the WLUN sdev_gendev member is used to control runtime power management of the UFS host controller. Checking whether or not the hba->ufs_device_wlun pointer is NULL from the ufshcd_rtc_work() function would be racy since that pointer is modified from another thread. So I prefer the patch at the start of this thread instead of adding a hba->ufs_device_wlun pointer check. Thanks, Bart.
On Thu, 2024-10-31 at 14:26 -0700, Bart Van Assche wrote: > The RTC update work involves runtime resuming the UFS controller. > Hence, > only start the RTC update work after runtime power management in the > UFS > driver has been fully initialized. This patch fixes the following > kernel > crash: > > Internal error: Oops: 0000000096000006 [#1] PREEMPT SMP > Workqueue: events ufshcd_rtc_work > Call trace: > _raw_spin_lock_irqsave+0x34/0x8c (P) > pm_runtime_get_if_active+0x24/0x9c (L) > pm_runtime_get_if_active+0x24/0x9c > ufshcd_rtc_work+0x138/0x1b4 > process_one_work+0x148/0x288 > worker_thread+0x2cc/0x3d4 > kthread+0x110/0x114 > ret_from_fork+0x10/0x20 > > Reported-by: Neil Armstrong <neil.armstrong@linaro.org> > Closes: > https://lore.kernel.org/linux-scsi/0c0bc528-fdc2-4106-bc99-f23ae377f6f5@linaro.org/ > Fixes: 6bf999e0eb41 ("scsi: ufs: core: Add UFS RTC support") > Cc: Bean Huo <beanhuo@micron.com> > Cc: stable@vger.kernel.org > Signed-off-by: Bart Van Assche <bvanassche@acm.org> Reviewed-by: Bean Huo <beanhuo@micron.com>
On Fri, Nov 01, 2024 at 09:31:27AM -0700, Bart Van Assche wrote: > On 11/1/24 12:53 AM, Manivannan Sadhasivam wrote: > > On Thu, Oct 31, 2024 at 02:26:24PM -0700, Bart Van Assche wrote: > > > The RTC update work involves runtime resuming the UFS controller. Hence, > > > only start the RTC update work after runtime power management in the UFS > > > driver has been fully initialized. This patch fixes the following kernel > > > crash: > > > > > > Internal error: Oops: 0000000096000006 [#1] PREEMPT SMP > > > Workqueue: events ufshcd_rtc_work > > > Call trace: > > > _raw_spin_lock_irqsave+0x34/0x8c (P) > > > pm_runtime_get_if_active+0x24/0x9c (L) > > > pm_runtime_get_if_active+0x24/0x9c > > > ufshcd_rtc_work+0x138/0x1b4 > > > process_one_work+0x148/0x288 > > > worker_thread+0x2cc/0x3d4 > > > kthread+0x110/0x114 > > > ret_from_fork+0x10/0x20 > > > > > > Reported-by: Neil Armstrong <neil.armstrong@linaro.org> > > > Closes: https://lore.kernel.org/linux-scsi/0c0bc528-fdc2-4106-bc99-f23ae377f6f5@linaro.org/ > > > Fixes: 6bf999e0eb41 ("scsi: ufs: core: Add UFS RTC support") > > > Cc: Bean Huo <beanhuo@micron.com> > > > Cc: stable@vger.kernel.org > > > Signed-off-by: Bart Van Assche <bvanassche@acm.org> > > > > Bart, Thanks for the fix! While looking into this patch, I also found the > > weirdness of the ufshcd_rpm_*() helpers in ufshcd-priv.h. Their naming doesn't > > seem to indicate whether those helpers are for WLUN or for HBA. Also, I don't > > see the benefit of these helpers since they just wrap generic pm_runtime* > > calls. Then there are other open coding instances in the ufshcd.c. Like > > > > pm_runtime_suspended(&hba->ufs_device_wlun->sdev_gendev) > > pm_runtime_set_active(&hba->ufs_device_wlun->sdev_gendev) > > > > Moreover, we do check for the presence of hba->ufs_device_wlun before calling > > ufshcd_rpm_get_sync() in ufshcd_remove(). This could be one other way to fix > > this null ptr dereference even though I wouldn't recommend doing so as calling > > rtc_work early is pointless. > > > > So I think we should remove these helpers to avoid having these discrepancies. > > WDYT? > > Hi Manivannan, > > In the context of the Linux kernel, in general, one-line helper > functions are considered questionable. In this case I prefer to keep the > helper functions since these encapsulate an implementation detail, > namely that the WLUN sdev_gendev member is used to control runtime power > management of the UFS host controller. > IMO this encapsulation is causing confusion since we have a separate PM handling for the UFS controller itself. > Checking whether or not the hba->ufs_device_wlun pointer is NULL from > the ufshcd_rtc_work() function would be racy since that pointer is modified > from another thread. So I prefer the patch at the start of this > thread instead of adding a hba->ufs_device_wlun pointer check. > Absolutely! I just pointed out it as a bad example which one could think of due to these helpers. - Mani
diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c index 585557eaa9a2..ed82ff329314 100644 --- a/drivers/ufs/core/ufshcd.c +++ b/drivers/ufs/core/ufshcd.c @@ -8633,6 +8633,14 @@ static int ufshcd_add_lus(struct ufs_hba *hba) ufshcd_init_clk_scaling_sysfs(hba); } + /* + * The RTC update code accesses the hba->ufs_device_wlun->sdev_gendev + * pointer and hence must only be started after the WLUN pointer has + * been initialized by ufshcd_scsi_add_wlus(). + */ + schedule_delayed_work(&hba->ufs_rtc_update_work, + msecs_to_jiffies(UFS_RTC_UPDATE_INTERVAL_MS)); + ufs_bsg_probe(hba); scsi_scan_host(hba->host); @@ -8727,8 +8735,6 @@ static int ufshcd_post_device_init(struct ufs_hba *hba) ufshcd_force_reset_auto_bkops(hba); ufshcd_set_timestamp_attr(hba); - schedule_delayed_work(&hba->ufs_rtc_update_work, - msecs_to_jiffies(UFS_RTC_UPDATE_INTERVAL_MS)); if (!hba->max_pwr_info.is_valid) return 0;
The RTC update work involves runtime resuming the UFS controller. Hence, only start the RTC update work after runtime power management in the UFS driver has been fully initialized. This patch fixes the following kernel crash: Internal error: Oops: 0000000096000006 [#1] PREEMPT SMP Workqueue: events ufshcd_rtc_work Call trace: _raw_spin_lock_irqsave+0x34/0x8c (P) pm_runtime_get_if_active+0x24/0x9c (L) pm_runtime_get_if_active+0x24/0x9c ufshcd_rtc_work+0x138/0x1b4 process_one_work+0x148/0x288 worker_thread+0x2cc/0x3d4 kthread+0x110/0x114 ret_from_fork+0x10/0x20 Reported-by: Neil Armstrong <neil.armstrong@linaro.org> Closes: https://lore.kernel.org/linux-scsi/0c0bc528-fdc2-4106-bc99-f23ae377f6f5@linaro.org/ Fixes: 6bf999e0eb41 ("scsi: ufs: core: Add UFS RTC support") Cc: Bean Huo <beanhuo@micron.com> Cc: stable@vger.kernel.org Signed-off-by: Bart Van Assche <bvanassche@acm.org> --- drivers/ufs/core/ufshcd.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)