| Message ID | 20200728075102.30807-1-saiprakash.ranjan@codeaurora.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [PATCHv2] coresight: etm4x: Fix etm4_count race by moving cpuhp callbacks to init | expand |
Quoting Sai Prakash Ranjan (2020-07-28 00:51:02) > diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c > index 6d7d2169bfb2..adb71987a1e3 100644 > --- a/drivers/hwtracing/coresight/coresight-etm4x.c > +++ b/drivers/hwtracing/coresight/coresight-etm4x.c > @@ -48,8 +48,6 @@ module_param(pm_save_enable, int, 0444); > MODULE_PARM_DESC(pm_save_enable, > "Save/restore state on power down: 1 = never, 2 = self-hosted"); > > -/* The number of ETMv4 currently registered */ > -static int etm4_count; > static struct etmv4_drvdata *etmdrvdata[NR_CPUS]; > static void etm4_set_default_config(struct etmv4_config *config); > static int etm4_set_event_filters(struct etmv4_drvdata *drvdata, > @@ -1403,12 +1401,9 @@ static int etm4_pm_setup_cpuslocked(void) Is this only called from __init now? If so please mark it as __init then. > { > int ret; > > - if (etm4_count++) > - return 0; > - > ret = cpu_pm_register_notifier(&etm4_cpu_pm_nb); > if (ret) > - goto reduce_count; > + return ret; > > ret = cpuhp_setup_state_nocalls_cpuslocked(CPUHP_AP_ARM_CORESIGHT_STARTING, > "arm/coresight4:starting", > @@ -1432,17 +1427,11 @@ static int etm4_pm_setup_cpuslocked(void) > > unregister_notifier: > cpu_pm_unregister_notifier(&etm4_cpu_pm_nb); > - > -reduce_count: > - --etm4_count; > return ret; > } > > static void etm4_pm_clear(void) This is __init too? > { > - if (--etm4_count != 0) > - return; > - > cpu_pm_unregister_notifier(&etm4_cpu_pm_nb); > cpuhp_remove_state_nocalls(CPUHP_AP_ARM_CORESIGHT_STARTING); > if (hp_online) { > @@ -1598,4 +1576,29 @@ static struct amba_driver etm4x_driver = { > .probe = etm4_probe, > .id_table = etm4_ids, > }; > -builtin_amba_driver(etm4x_driver); > + > +static int __init etm4x_init(void) > +{ > + int ret; > + > + cpus_read_lock(); > + ret = etm4_pm_setup_cpuslocked(); > + cpus_read_unlock(); > + > + /* etm4_pm_setup_cpuslocked() does its own cleanup - exit on error */ > + if (ret) > + return ret; > + > + ret = amba_driver_register(&etm4x_driver); > + if (ret) { > + pr_info("Error registering etm4x driver\n"); Use pr_err() please. > + goto err_init; > + } > + > + return ret; > + > +err_init: Why is this a goto? > + etm4_pm_clear(); > + return ret; Instead of just putting this in the if (ret) arm? > +} > +module_init(etm4x_init); It was device_initcall before with builtin_amba_driver(), best to not change that.
On 2020-07-28 13:59, Stephen Boyd wrote: > Quoting Sai Prakash Ranjan (2020-07-28 00:51:02) >> diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c >> b/drivers/hwtracing/coresight/coresight-etm4x.c >> index 6d7d2169bfb2..adb71987a1e3 100644 >> --- a/drivers/hwtracing/coresight/coresight-etm4x.c >> +++ b/drivers/hwtracing/coresight/coresight-etm4x.c >> @@ -48,8 +48,6 @@ module_param(pm_save_enable, int, 0444); >> MODULE_PARM_DESC(pm_save_enable, >> "Save/restore state on power down: 1 = never, 2 = >> self-hosted"); >> >> -/* The number of ETMv4 currently registered */ >> -static int etm4_count; >> static struct etmv4_drvdata *etmdrvdata[NR_CPUS]; >> static void etm4_set_default_config(struct etmv4_config *config); >> static int etm4_set_event_filters(struct etmv4_drvdata *drvdata, >> @@ -1403,12 +1401,9 @@ static int etm4_pm_setup_cpuslocked(void) > > Is this only called from __init now? If so please mark it as __init > then. > Yes, will change it. >> { >> int ret; >> >> - if (etm4_count++) >> - return 0; >> - >> ret = cpu_pm_register_notifier(&etm4_cpu_pm_nb); >> if (ret) >> - goto reduce_count; >> + return ret; >> >> ret = >> cpuhp_setup_state_nocalls_cpuslocked(CPUHP_AP_ARM_CORESIGHT_STARTING, >> >> "arm/coresight4:starting", >> @@ -1432,17 +1427,11 @@ static int etm4_pm_setup_cpuslocked(void) >> >> unregister_notifier: >> cpu_pm_unregister_notifier(&etm4_cpu_pm_nb); >> - >> -reduce_count: >> - --etm4_count; >> return ret; >> } >> >> static void etm4_pm_clear(void) > > This is __init too? > Will change. >> { >> - if (--etm4_count != 0) >> - return; >> - >> cpu_pm_unregister_notifier(&etm4_cpu_pm_nb); >> cpuhp_remove_state_nocalls(CPUHP_AP_ARM_CORESIGHT_STARTING); >> if (hp_online) { >> @@ -1598,4 +1576,29 @@ static struct amba_driver etm4x_driver = { >> .probe = etm4_probe, >> .id_table = etm4_ids, >> }; >> -builtin_amba_driver(etm4x_driver); >> + >> +static int __init etm4x_init(void) >> +{ >> + int ret; >> + >> + cpus_read_lock(); >> + ret = etm4_pm_setup_cpuslocked(); >> + cpus_read_unlock(); >> + >> + /* etm4_pm_setup_cpuslocked() does its own cleanup - exit on >> error */ >> + if (ret) >> + return ret; >> + >> + ret = amba_driver_register(&etm4x_driver); >> + if (ret) { >> + pr_info("Error registering etm4x driver\n"); > > Use pr_err() please. > Yes indeed, will change. >> + goto err_init; >> + } >> + >> + return ret; >> + >> +err_init: > > Why is this a goto? > >> + etm4_pm_clear(); >> + return ret; > > Instead of just putting this in the if (ret) arm? > Will change. >> +} >> +module_init(etm4x_init); > > It was device_initcall before with builtin_amba_driver(), best to not > change that. Sure. I will wait to see if there are any more comments on this patch and then post a v3. Thanks for the review Stephen. Thanks, Sai
Hi Sai, On Tue, 28 Jul 2020 at 08:51, Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org> wrote: > > etm4_count keeps track of number of ETMv4 registered and on some systems, > a race is observed on etm4_count variable which can lead to multiple calls > to cpuhp_setup_state_nocalls_cpuslocked(). This function internally calls > cpuhp_store_callbacks() which prevents multiple registrations of callbacks > for a given state and due to this race, it returns -EBUSY leading to ETM > probe failures like below. > > coresight-etm4x: probe of 7040000.etm failed with error -16 > > This race can easily be triggered with async probe by setting probe type > as PROBE_PREFER_ASYNCHRONOUS and with ETM power management property > "arm,coresight-loses-context-with-cpu". > > Prevent this race by moving cpuhp callbacks to etm driver init since the > cpuhp callbacks doesn't have to depend on the etm4_count and can be once > setup during driver init. Similarly we move cpu_pm notifier registration > to driver init and completely remove etm4_count usage. > > Fixes: 9b6a3f3633a5 ("coresight: etmv4: Fix CPU power management setup in probe() function") > Fixes: 58eb457be028 ("hwtracing/coresight-etm4x: Convert to hotplug state machine") > Suggested-by: Suzuki K Poulose <suzuki.poulose@arm.com> > Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org> > --- > > Changes in v2: > * Rearrange cpuhp callbacks and move them to driver init (Suzuki K Poulose) > > --- > drivers/hwtracing/coresight/coresight-etm4x.c | 51 ++++++++++--------- > 1 file changed, 27 insertions(+), 24 deletions(-) > > diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c > index 6d7d2169bfb2..adb71987a1e3 100644 > --- a/drivers/hwtracing/coresight/coresight-etm4x.c > +++ b/drivers/hwtracing/coresight/coresight-etm4x.c > @@ -48,8 +48,6 @@ module_param(pm_save_enable, int, 0444); > MODULE_PARM_DESC(pm_save_enable, > "Save/restore state on power down: 1 = never, 2 = self-hosted"); > > -/* The number of ETMv4 currently registered */ > -static int etm4_count; > static struct etmv4_drvdata *etmdrvdata[NR_CPUS]; > static void etm4_set_default_config(struct etmv4_config *config); > static int etm4_set_event_filters(struct etmv4_drvdata *drvdata, > @@ -1403,12 +1401,9 @@ static int etm4_pm_setup_cpuslocked(void) > { consider renaming this to etm4_pm_setup() and handing any cpu locking inside the function. In the circumstances - as part of the driver init rather than probe it may be sufficient to call the cpuhp_setup functions without the _cpuslocked suffix and allow the calls to lock the cpus as they are made. i.e. cpuhp_setup_state_nocalls_cpuslocked() => cpuhp_setup_state_nocalls() > int ret; > > - if (etm4_count++) > - return 0; > - > ret = cpu_pm_register_notifier(&etm4_cpu_pm_nb); > if (ret) > - goto reduce_count; > + return ret; > > ret = cpuhp_setup_state_nocalls_cpuslocked(CPUHP_AP_ARM_CORESIGHT_STARTING, > "arm/coresight4:starting", > @@ -1432,17 +1427,11 @@ static int etm4_pm_setup_cpuslocked(void) > > unregister_notifier: > cpu_pm_unregister_notifier(&etm4_cpu_pm_nb); > - > -reduce_count: > - --etm4_count; > return ret; > } > > static void etm4_pm_clear(void) > { > - if (--etm4_count != 0) > - return; > - > cpu_pm_unregister_notifier(&etm4_cpu_pm_nb); > cpuhp_remove_state_nocalls(CPUHP_AP_ARM_CORESIGHT_STARTING); > if (hp_online) { > @@ -1498,22 +1487,12 @@ static int etm4_probe(struct amba_device *adev, const struct amba_id *id) > if (!desc.name) > return -ENOMEM; > > - cpus_read_lock(); > etmdrvdata[drvdata->cpu] = drvdata; > > if (smp_call_function_single(drvdata->cpu, > etm4_init_arch_data, drvdata, 1)) > dev_err(dev, "ETM arch init failed\n"); > > - ret = etm4_pm_setup_cpuslocked(); > - cpus_read_unlock(); > - > - /* etm4_pm_setup_cpuslocked() does its own cleanup - exit on error */ > - if (ret) { > - etmdrvdata[drvdata->cpu] = NULL; > - return ret; > - } > - > if (etm4_arch_supported(drvdata->arch) == false) { > ret = -EINVAL; > goto err_arch_supported; > @@ -1560,7 +1539,6 @@ static int etm4_probe(struct amba_device *adev, const struct amba_id *id) > > err_arch_supported: > etmdrvdata[drvdata->cpu] = NULL; > - etm4_pm_clear(); > return ret; > } > > @@ -1598,4 +1576,29 @@ static struct amba_driver etm4x_driver = { > .probe = etm4_probe, > .id_table = etm4_ids, > }; > -builtin_amba_driver(etm4x_driver); > + > +static int __init etm4x_init(void) > +{ > + int ret; > + > + cpus_read_lock(); > + ret = etm4_pm_setup_cpuslocked(); > + cpus_read_unlock(); See my comment above about rename and use of cpus_read_lock Regards Mike > + > + /* etm4_pm_setup_cpuslocked() does its own cleanup - exit on error */ > + if (ret) > + return ret; > + > + ret = amba_driver_register(&etm4x_driver); > + if (ret) { > + pr_info("Error registering etm4x driver\n"); > + goto err_init; > + } > + > + return ret; > + > +err_init: > + etm4_pm_clear(); > + return ret; > +} > +module_init(etm4x_init); > -- > QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member > of Code Aurora Forum, hosted by The Linux Foundation > > _______________________________________________ > CoreSight mailing list > CoreSight@lists.linaro.org > https://lists.linaro.org/mailman/listinfo/coresight
Hi Mike, On 2020-07-29 01:46, Mike Leach wrote: > Hi Sai, > > On Tue, 28 Jul 2020 at 08:51, Sai Prakash Ranjan > <saiprakash.ranjan@codeaurora.org> wrote: >> >> etm4_count keeps track of number of ETMv4 registered and on some >> systems, >> a race is observed on etm4_count variable which can lead to multiple >> calls >> to cpuhp_setup_state_nocalls_cpuslocked(). This function internally >> calls >> cpuhp_store_callbacks() which prevents multiple registrations of >> callbacks >> for a given state and due to this race, it returns -EBUSY leading to >> ETM >> probe failures like below. >> >> coresight-etm4x: probe of 7040000.etm failed with error -16 >> >> This race can easily be triggered with async probe by setting probe >> type >> as PROBE_PREFER_ASYNCHRONOUS and with ETM power management property >> "arm,coresight-loses-context-with-cpu". >> >> Prevent this race by moving cpuhp callbacks to etm driver init since >> the >> cpuhp callbacks doesn't have to depend on the etm4_count and can be >> once >> setup during driver init. Similarly we move cpu_pm notifier >> registration >> to driver init and completely remove etm4_count usage. >> >> Fixes: 9b6a3f3633a5 ("coresight: etmv4: Fix CPU power management setup >> in probe() function") >> Fixes: 58eb457be028 ("hwtracing/coresight-etm4x: Convert to hotplug >> state machine") >> Suggested-by: Suzuki K Poulose <suzuki.poulose@arm.com> >> Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org> >> --- >> >> Changes in v2: >> * Rearrange cpuhp callbacks and move them to driver init (Suzuki K >> Poulose) >> >> --- >> drivers/hwtracing/coresight/coresight-etm4x.c | 51 >> ++++++++++--------- >> 1 file changed, 27 insertions(+), 24 deletions(-) >> >> diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c >> b/drivers/hwtracing/coresight/coresight-etm4x.c >> index 6d7d2169bfb2..adb71987a1e3 100644 >> --- a/drivers/hwtracing/coresight/coresight-etm4x.c >> +++ b/drivers/hwtracing/coresight/coresight-etm4x.c >> @@ -48,8 +48,6 @@ module_param(pm_save_enable, int, 0444); >> MODULE_PARM_DESC(pm_save_enable, >> "Save/restore state on power down: 1 = never, 2 = >> self-hosted"); >> >> -/* The number of ETMv4 currently registered */ >> -static int etm4_count; >> static struct etmv4_drvdata *etmdrvdata[NR_CPUS]; >> static void etm4_set_default_config(struct etmv4_config *config); >> static int etm4_set_event_filters(struct etmv4_drvdata *drvdata, >> @@ -1403,12 +1401,9 @@ static int etm4_pm_setup_cpuslocked(void) >> { > > consider renaming this to etm4_pm_setup() and handing any cpu locking > inside the function. > In the circumstances - as part of the driver init rather than probe it > may be sufficient to call the cpuhp_setup functions without the > _cpuslocked suffix and allow the calls to lock the cpus as they are > made. > i.e. cpuhp_setup_state_nocalls_cpuslocked() => > cpuhp_setup_state_nocalls() Sure, will make this change. > >> int ret; >> >> - if (etm4_count++) >> - return 0; >> - >> ret = cpu_pm_register_notifier(&etm4_cpu_pm_nb); >> if (ret) >> - goto reduce_count; >> + return ret; >> >> ret = >> cpuhp_setup_state_nocalls_cpuslocked(CPUHP_AP_ARM_CORESIGHT_STARTING, >> >> "arm/coresight4:starting", >> @@ -1432,17 +1427,11 @@ static int etm4_pm_setup_cpuslocked(void) >> >> unregister_notifier: >> cpu_pm_unregister_notifier(&etm4_cpu_pm_nb); >> - >> -reduce_count: >> - --etm4_count; >> return ret; >> } >> >> static void etm4_pm_clear(void) >> { >> - if (--etm4_count != 0) >> - return; >> - >> cpu_pm_unregister_notifier(&etm4_cpu_pm_nb); >> cpuhp_remove_state_nocalls(CPUHP_AP_ARM_CORESIGHT_STARTING); >> if (hp_online) { >> @@ -1498,22 +1487,12 @@ static int etm4_probe(struct amba_device >> *adev, const struct amba_id *id) >> if (!desc.name) >> return -ENOMEM; >> >> - cpus_read_lock(); >> etmdrvdata[drvdata->cpu] = drvdata; >> >> if (smp_call_function_single(drvdata->cpu, >> etm4_init_arch_data, drvdata, 1)) >> dev_err(dev, "ETM arch init failed\n"); >> >> - ret = etm4_pm_setup_cpuslocked(); >> - cpus_read_unlock(); >> - >> - /* etm4_pm_setup_cpuslocked() does its own cleanup - exit on >> error */ >> - if (ret) { >> - etmdrvdata[drvdata->cpu] = NULL; >> - return ret; >> - } >> - >> if (etm4_arch_supported(drvdata->arch) == false) { >> ret = -EINVAL; >> goto err_arch_supported; >> @@ -1560,7 +1539,6 @@ static int etm4_probe(struct amba_device *adev, >> const struct amba_id *id) >> >> err_arch_supported: >> etmdrvdata[drvdata->cpu] = NULL; >> - etm4_pm_clear(); >> return ret; >> } >> >> @@ -1598,4 +1576,29 @@ static struct amba_driver etm4x_driver = { >> .probe = etm4_probe, >> .id_table = etm4_ids, >> }; >> -builtin_amba_driver(etm4x_driver); >> + >> +static int __init etm4x_init(void) >> +{ >> + int ret; >> + >> + cpus_read_lock(); >> + ret = etm4_pm_setup_cpuslocked(); >> + cpus_read_unlock(); > > See my comment above about rename and use of cpus_read_lock > Yes, thanks for the review Mike. Thanks, Sai
diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c index 6d7d2169bfb2..adb71987a1e3 100644 --- a/drivers/hwtracing/coresight/coresight-etm4x.c +++ b/drivers/hwtracing/coresight/coresight-etm4x.c @@ -48,8 +48,6 @@ module_param(pm_save_enable, int, 0444); MODULE_PARM_DESC(pm_save_enable, "Save/restore state on power down: 1 = never, 2 = self-hosted"); -/* The number of ETMv4 currently registered */ -static int etm4_count; static struct etmv4_drvdata *etmdrvdata[NR_CPUS]; static void etm4_set_default_config(struct etmv4_config *config); static int etm4_set_event_filters(struct etmv4_drvdata *drvdata, @@ -1403,12 +1401,9 @@ static int etm4_pm_setup_cpuslocked(void) { int ret; - if (etm4_count++) - return 0; - ret = cpu_pm_register_notifier(&etm4_cpu_pm_nb); if (ret) - goto reduce_count; + return ret; ret = cpuhp_setup_state_nocalls_cpuslocked(CPUHP_AP_ARM_CORESIGHT_STARTING, "arm/coresight4:starting", @@ -1432,17 +1427,11 @@ static int etm4_pm_setup_cpuslocked(void) unregister_notifier: cpu_pm_unregister_notifier(&etm4_cpu_pm_nb); - -reduce_count: - --etm4_count; return ret; } static void etm4_pm_clear(void) { - if (--etm4_count != 0) - return; - cpu_pm_unregister_notifier(&etm4_cpu_pm_nb); cpuhp_remove_state_nocalls(CPUHP_AP_ARM_CORESIGHT_STARTING); if (hp_online) { @@ -1498,22 +1487,12 @@ static int etm4_probe(struct amba_device *adev, const struct amba_id *id) if (!desc.name) return -ENOMEM; - cpus_read_lock(); etmdrvdata[drvdata->cpu] = drvdata; if (smp_call_function_single(drvdata->cpu, etm4_init_arch_data, drvdata, 1)) dev_err(dev, "ETM arch init failed\n"); - ret = etm4_pm_setup_cpuslocked(); - cpus_read_unlock(); - - /* etm4_pm_setup_cpuslocked() does its own cleanup - exit on error */ - if (ret) { - etmdrvdata[drvdata->cpu] = NULL; - return ret; - } - if (etm4_arch_supported(drvdata->arch) == false) { ret = -EINVAL; goto err_arch_supported; @@ -1560,7 +1539,6 @@ static int etm4_probe(struct amba_device *adev, const struct amba_id *id) err_arch_supported: etmdrvdata[drvdata->cpu] = NULL; - etm4_pm_clear(); return ret; } @@ -1598,4 +1576,29 @@ static struct amba_driver etm4x_driver = { .probe = etm4_probe, .id_table = etm4_ids, }; -builtin_amba_driver(etm4x_driver); + +static int __init etm4x_init(void) +{ + int ret; + + cpus_read_lock(); + ret = etm4_pm_setup_cpuslocked(); + cpus_read_unlock(); + + /* etm4_pm_setup_cpuslocked() does its own cleanup - exit on error */ + if (ret) + return ret; + + ret = amba_driver_register(&etm4x_driver); + if (ret) { + pr_info("Error registering etm4x driver\n"); + goto err_init; + } + + return ret; + +err_init: + etm4_pm_clear(); + return ret; +} +module_init(etm4x_init);
etm4_count keeps track of number of ETMv4 registered and on some systems, a race is observed on etm4_count variable which can lead to multiple calls to cpuhp_setup_state_nocalls_cpuslocked(). This function internally calls cpuhp_store_callbacks() which prevents multiple registrations of callbacks for a given state and due to this race, it returns -EBUSY leading to ETM probe failures like below. coresight-etm4x: probe of 7040000.etm failed with error -16 This race can easily be triggered with async probe by setting probe type as PROBE_PREFER_ASYNCHRONOUS and with ETM power management property "arm,coresight-loses-context-with-cpu". Prevent this race by moving cpuhp callbacks to etm driver init since the cpuhp callbacks doesn't have to depend on the etm4_count and can be once setup during driver init. Similarly we move cpu_pm notifier registration to driver init and completely remove etm4_count usage. Fixes: 9b6a3f3633a5 ("coresight: etmv4: Fix CPU power management setup in probe() function") Fixes: 58eb457be028 ("hwtracing/coresight-etm4x: Convert to hotplug state machine") Suggested-by: Suzuki K Poulose <suzuki.poulose@arm.com> Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org> --- Changes in v2: * Rearrange cpuhp callbacks and move them to driver init (Suzuki K Poulose) --- drivers/hwtracing/coresight/coresight-etm4x.c | 51 ++++++++++--------- 1 file changed, 27 insertions(+), 24 deletions(-)