| Message ID | 1452533760-13787-7-git-send-email-juri.lelli@arm.com (mailing list archive) |
|---|---|
| State | RFC |
| Headers | show |
On 11-01-16, 17:35, Juri Lelli wrote: > Commit highlights paths where we access cpufreq_policy_list without > holding cpufreq_driver_lock; one example being the following: > > [ 8.245779] ------------[ cut here ]------------ > [ 8.305977] WARNING: CPU: 2 PID: 1 at kernel/drivers/cpufreq/cpufreq.c:2447 cpufreq_register_driver+0xfd/0x120() > [ 8.438611] Modules linked in: > [ 8.493751] CPU: 2 PID: 1 Comm: swapper/0 Not tainted 4.4.0-rc4+ #369 > [ 8.561039] Hardware name: ARM-Versatile Express > [ 8.622765] [<c0014215>] (unwind_backtrace) from [<c0010e25>] (show_stack+0x11/0x14) > [ 8.629651] atkbd serio0: keyboard reset failed on 1c060000.kmi > [ 8.810905] [<c0010e25>] (show_stack) from [<c02ece7d>] (dump_stack+0x55/0x78) > [ 8.935122] [<c02ece7d>] (dump_stack) from [<c00202cd>] (warn_slowpath_common+0x59/0x84) > [ 9.067097] [<c00202cd>] (warn_slowpath_common) from [<c002030f>] (warn_slowpath_null+0x17/0x1c) > [ 9.204101] [<c002030f>] (warn_slowpath_null) from [<c03ba329>] (cpufreq_register_driver+0xfd/0x120) > [ 9.209603] usb 1-1.2: new high-speed USB device number 3 using isp1760 > [ 9.419507] [<c03ba329>] (cpufreq_register_driver) from [<c03bc481>] (bL_cpufreq_register+0x49/0x98) > [ 9.560548] [<c03bc481>] (bL_cpufreq_register) from [<c0342517>] (platform_drv_probe+0x3b/0x6c) > [ 9.573806] usb-storage 1-1.2:1.0: USB Mass Storage device detected > [ 9.575468] scsi host0: usb-storage 1-1.2:1.0 > [ 9.855845] [<c0342517>] (platform_drv_probe) from [<c03412e7>] (driver_probe_device+0x153/0x1bc) > [ 10.006137] [<c03412e7>] (driver_probe_device) from [<c03413a7>] (__driver_attach+0x57/0x58) > [ 10.009576] atkbd serio1: keyboard reset failed on 1c070000.kmi > [ 10.237057] [<c03413a7>] (__driver_attach) from [<c0340199>] (bus_for_each_dev+0x2d/0x4c) > [ 10.387824] [<c0340199>] (bus_for_each_dev) from [<c0340bd7>] (bus_add_driver+0xa3/0x14c) > [ 10.539200] [<c0340bd7>] (bus_add_driver) from [<c0341bff>] (driver_register+0x3b/0x88) > [ 10.691023] [<c0341bff>] (driver_register) from [<c0009613>] (do_one_initcall+0x5b/0x150) > [ 10.703809] scsi 0:0:0:0: Direct-Access General USB Flash Disk 1.0 PQ: 0 ANSI: 2 > [ 10.713081] sd 0:0:0:0: [sda] 7831552 512-byte logical blocks: (4.00 GB/3.73 GiB) > [ 10.713973] sd 0:0:0:0: [sda] Write Protect is off > [ 10.713984] sd 0:0:0:0: [sda] Mode Sense: 03 00 00 00 > [ 10.730783] sd 0:0:0:0: [sda] No Caching mode page found > [ 10.730814] sd 0:0:0:0: [sda] Assuming drive cache: write through > [ 10.779815] sda: sda1 sda2 > [ 10.823590] sd 0:0:0:0: [sda] Attached SCSI removable disk > [ 11.581894] [<c0009613>] (do_one_initcall) from [<c0734b45>] (kernel_init_freeable+0x18d/0x22c) > [ 11.720454] [<c0734b45>] (kernel_init_freeable) from [<c04f45f9>] (kernel_init+0xd/0xa4) > [ 11.857340] [<c04f45f9>] (kernel_init) from [<c000dfb9>] (ret_from_fork+0x11/0x38) > [ 11.993082] ---[ end trace 62ff5522fb3f41dd ]--- > > Fix this, and others, with proper locking of cpufreq_driver_lock. Perhaps this should be added prior to the lockdep patch, so that git bisect doesn't show lockdeps ? > Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> > Cc: Viresh Kumar <viresh.kumar@linaro.org> > Signed-off-by: Juri Lelli <juri.lelli@arm.com> > --- > drivers/cpufreq/cpufreq.c | 13 ++++++++++++- > 1 file changed, 12 insertions(+), 1 deletion(-) > > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c > index 63d6efb..98adbc2 100644 > --- a/drivers/cpufreq/cpufreq.c > +++ b/drivers/cpufreq/cpufreq.c > @@ -1585,6 +1585,7 @@ EXPORT_SYMBOL(cpufreq_generic_suspend); > void cpufreq_suspend(void) > { > struct cpufreq_policy *policy; > + unsigned long flags; > > if (!cpufreq_driver) > return; > @@ -1594,6 +1595,7 @@ void cpufreq_suspend(void) > > pr_debug("%s: Suspending Governors\n", __func__); > > + read_lock_irqsave(&cpufreq_driver_lock, flags); > for_each_active_policy(policy) { > if (__cpufreq_governor(policy, CPUFREQ_GOV_STOP)) > pr_err("%s: Failed to stop governor for policy: %p\n", > @@ -1603,6 +1605,7 @@ void cpufreq_suspend(void) > pr_err("%s: Failed to suspend driver: %p\n", __func__, > policy); > } > + read_unlock_irqrestore(&cpufreq_driver_lock, flags); > > suspend: > cpufreq_suspended = true; > @@ -1617,6 +1620,7 @@ suspend: > void cpufreq_resume(void) > { > struct cpufreq_policy *policy; > + unsigned long flags; > > if (!cpufreq_driver) > return; > @@ -1628,6 +1632,7 @@ void cpufreq_resume(void) > > pr_debug("%s: Resuming Governors\n", __func__); > > + read_lock_irqsave(&cpufreq_driver_lock, flags); > for_each_active_policy(policy) { > if (cpufreq_driver->resume && cpufreq_driver->resume(policy)) > pr_err("%s: Failed to resume driver: %p\n", __func__, > @@ -1637,6 +1642,7 @@ void cpufreq_resume(void) > pr_err("%s: Failed to start governor for policy: %p\n", > __func__, policy); > } > + read_unlock_irqrestore(&cpufreq_driver_lock, flags); > > /* > * schedule call cpufreq_update_policy() for first-online CPU, as that > @@ -2287,7 +2293,9 @@ static int cpufreq_boost_set_sw(int state) > struct cpufreq_frequency_table *freq_table; > struct cpufreq_policy *policy; > int ret = -EINVAL; > + unsigned long flags; > > + read_lock_irqsave(&cpufreq_driver_lock, flags); > for_each_active_policy(policy) { > freq_table = cpufreq_frequency_get_table(policy->cpu); > if (freq_table) { > @@ -2302,6 +2310,7 @@ static int cpufreq_boost_set_sw(int state) > __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS); > } > } > + read_unlock_irqrestore(&cpufreq_driver_lock, flags); > > return ret; > } For the above three, I am not sure if there can be some side effects. Can you please push a branch somewhere, to be tested by Fengguang's build bot? So that we know of any new lockdeps due to this? All above routines directly/indirectly call governor specific routines and that leads to freq-update in few cases. AFAIR, there were some issues with locking here. > @@ -2432,14 +2441,16 @@ int cpufreq_register_driver(struct cpufreq_driver *driver_data) > if (ret) > goto err_boost_unreg; > > - lockdep_assert_held(&cpufreq_driver_lock); > + read_lock_irqsave(&cpufreq_driver_lock, flags); > if (!(cpufreq_driver->flags & CPUFREQ_STICKY) && > list_empty(&cpufreq_policy_list)) { > /* if all ->init() calls failed, unregister */ > pr_debug("%s: No CPU initialized for driver %s\n", __func__, > driver_data->name); > + read_unlock_irqrestore(&cpufreq_driver_lock, flags); > goto err_if_unreg; > } > + read_unlock_irqrestore(&cpufreq_driver_lock, flags); We have just registered the cpufreq driver, there is no other path that can simultaneously update the list here. And so we don't need the lock here.
Hi, On 12/01/16 15:27, Viresh Kumar wrote: > On 11-01-16, 17:35, Juri Lelli wrote: > > Commit highlights paths where we access cpufreq_policy_list without > > holding cpufreq_driver_lock; one example being the following: > > > > [ 8.245779] ------------[ cut here ]------------ > > [ 8.305977] WARNING: CPU: 2 PID: 1 at kernel/drivers/cpufreq/cpufreq.c:2447 cpufreq_register_driver+0xfd/0x120() > > [ 8.438611] Modules linked in: > > [ 8.493751] CPU: 2 PID: 1 Comm: swapper/0 Not tainted 4.4.0-rc4+ #369 > > [ 8.561039] Hardware name: ARM-Versatile Express > > [ 8.622765] [<c0014215>] (unwind_backtrace) from [<c0010e25>] (show_stack+0x11/0x14) > > [ 8.629651] atkbd serio0: keyboard reset failed on 1c060000.kmi > > [ 8.810905] [<c0010e25>] (show_stack) from [<c02ece7d>] (dump_stack+0x55/0x78) > > [ 8.935122] [<c02ece7d>] (dump_stack) from [<c00202cd>] (warn_slowpath_common+0x59/0x84) > > [ 9.067097] [<c00202cd>] (warn_slowpath_common) from [<c002030f>] (warn_slowpath_null+0x17/0x1c) > > [ 9.204101] [<c002030f>] (warn_slowpath_null) from [<c03ba329>] (cpufreq_register_driver+0xfd/0x120) > > [ 9.209603] usb 1-1.2: new high-speed USB device number 3 using isp1760 > > [ 9.419507] [<c03ba329>] (cpufreq_register_driver) from [<c03bc481>] (bL_cpufreq_register+0x49/0x98) > > [ 9.560548] [<c03bc481>] (bL_cpufreq_register) from [<c0342517>] (platform_drv_probe+0x3b/0x6c) > > [ 9.573806] usb-storage 1-1.2:1.0: USB Mass Storage device detected > > [ 9.575468] scsi host0: usb-storage 1-1.2:1.0 > > [ 9.855845] [<c0342517>] (platform_drv_probe) from [<c03412e7>] (driver_probe_device+0x153/0x1bc) > > [ 10.006137] [<c03412e7>] (driver_probe_device) from [<c03413a7>] (__driver_attach+0x57/0x58) > > [ 10.009576] atkbd serio1: keyboard reset failed on 1c070000.kmi > > [ 10.237057] [<c03413a7>] (__driver_attach) from [<c0340199>] (bus_for_each_dev+0x2d/0x4c) > > [ 10.387824] [<c0340199>] (bus_for_each_dev) from [<c0340bd7>] (bus_add_driver+0xa3/0x14c) > > [ 10.539200] [<c0340bd7>] (bus_add_driver) from [<c0341bff>] (driver_register+0x3b/0x88) > > [ 10.691023] [<c0341bff>] (driver_register) from [<c0009613>] (do_one_initcall+0x5b/0x150) > > [ 10.703809] scsi 0:0:0:0: Direct-Access General USB Flash Disk 1.0 PQ: 0 ANSI: 2 > > [ 10.713081] sd 0:0:0:0: [sda] 7831552 512-byte logical blocks: (4.00 GB/3.73 GiB) > > [ 10.713973] sd 0:0:0:0: [sda] Write Protect is off > > [ 10.713984] sd 0:0:0:0: [sda] Mode Sense: 03 00 00 00 > > [ 10.730783] sd 0:0:0:0: [sda] No Caching mode page found > > [ 10.730814] sd 0:0:0:0: [sda] Assuming drive cache: write through > > [ 10.779815] sda: sda1 sda2 > > [ 10.823590] sd 0:0:0:0: [sda] Attached SCSI removable disk > > [ 11.581894] [<c0009613>] (do_one_initcall) from [<c0734b45>] (kernel_init_freeable+0x18d/0x22c) > > [ 11.720454] [<c0734b45>] (kernel_init_freeable) from [<c04f45f9>] (kernel_init+0xd/0xa4) > > [ 11.857340] [<c04f45f9>] (kernel_init) from [<c000dfb9>] (ret_from_fork+0x11/0x38) > > [ 11.993082] ---[ end trace 62ff5522fb3f41dd ]--- > > > > Fix this, and others, with proper locking of cpufreq_driver_lock. > > Perhaps this should be added prior to the lockdep patch, so that git > bisect doesn't show lockdeps ? > I put patches in this order to be able to highlight problems before fixing them. But I agree this is not nice for bisectability. I guess I could squash related fixes and assertions together (when removing the RFC tag) so that we don't break bisectability. > > Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> > > Cc: Viresh Kumar <viresh.kumar@linaro.org> > > Signed-off-by: Juri Lelli <juri.lelli@arm.com> > > --- > > drivers/cpufreq/cpufreq.c | 13 ++++++++++++- > > 1 file changed, 12 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c > > index 63d6efb..98adbc2 100644 > > --- a/drivers/cpufreq/cpufreq.c > > +++ b/drivers/cpufreq/cpufreq.c > > @@ -1585,6 +1585,7 @@ EXPORT_SYMBOL(cpufreq_generic_suspend); > > void cpufreq_suspend(void) > > { > > struct cpufreq_policy *policy; > > + unsigned long flags; > > > > if (!cpufreq_driver) > > return; > > @@ -1594,6 +1595,7 @@ void cpufreq_suspend(void) > > > > pr_debug("%s: Suspending Governors\n", __func__); > > > > + read_lock_irqsave(&cpufreq_driver_lock, flags); > > for_each_active_policy(policy) { > > if (__cpufreq_governor(policy, CPUFREQ_GOV_STOP)) > > pr_err("%s: Failed to stop governor for policy: %p\n", > > @@ -1603,6 +1605,7 @@ void cpufreq_suspend(void) > > pr_err("%s: Failed to suspend driver: %p\n", __func__, > > policy); > > } > > + read_unlock_irqrestore(&cpufreq_driver_lock, flags); > > > > suspend: > > cpufreq_suspended = true; > > @@ -1617,6 +1620,7 @@ suspend: > > void cpufreq_resume(void) > > { > > struct cpufreq_policy *policy; > > + unsigned long flags; > > > > if (!cpufreq_driver) > > return; > > @@ -1628,6 +1632,7 @@ void cpufreq_resume(void) > > > > pr_debug("%s: Resuming Governors\n", __func__); > > > > + read_lock_irqsave(&cpufreq_driver_lock, flags); > > for_each_active_policy(policy) { > > if (cpufreq_driver->resume && cpufreq_driver->resume(policy)) > > pr_err("%s: Failed to resume driver: %p\n", __func__, > > @@ -1637,6 +1642,7 @@ void cpufreq_resume(void) > > pr_err("%s: Failed to start governor for policy: %p\n", > > __func__, policy); > > } > > + read_unlock_irqrestore(&cpufreq_driver_lock, flags); > > > > /* > > * schedule call cpufreq_update_policy() for first-online CPU, as that > > @@ -2287,7 +2293,9 @@ static int cpufreq_boost_set_sw(int state) > > struct cpufreq_frequency_table *freq_table; > > struct cpufreq_policy *policy; > > int ret = -EINVAL; > > + unsigned long flags; > > > > + read_lock_irqsave(&cpufreq_driver_lock, flags); > > for_each_active_policy(policy) { > > freq_table = cpufreq_frequency_get_table(policy->cpu); > > if (freq_table) { > > @@ -2302,6 +2310,7 @@ static int cpufreq_boost_set_sw(int state) > > __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS); > > } > > } > > + read_unlock_irqrestore(&cpufreq_driver_lock, flags); > > > > return ret; > > } > > For the above three, I am not sure if there can be some side effects. > Can you please push a branch somewhere, to be tested by Fengguang's > build bot? So that we know of any new lockdeps due to this? All above > routines directly/indirectly call governor specific routines and that > leads to freq-update in few cases. AFAIR, there were some issues with > locking here. > I currently don't have any branch fetched by Fengguang's bot; I'll see how to start doing that. In the meantime I'll try to setup an x86 box and run some more tests. > > @@ -2432,14 +2441,16 @@ int cpufreq_register_driver(struct cpufreq_driver *driver_data) > > if (ret) > > goto err_boost_unreg; > > > > - lockdep_assert_held(&cpufreq_driver_lock); > > + read_lock_irqsave(&cpufreq_driver_lock, flags); > > if (!(cpufreq_driver->flags & CPUFREQ_STICKY) && > > list_empty(&cpufreq_policy_list)) { > > /* if all ->init() calls failed, unregister */ > > pr_debug("%s: No CPU initialized for driver %s\n", __func__, > > driver_data->name); > > + read_unlock_irqrestore(&cpufreq_driver_lock, flags); > > goto err_if_unreg; > > } > > + read_unlock_irqrestore(&cpufreq_driver_lock, flags); > > We have just registered the cpufreq driver, there is no other path > that can simultaneously update the list here. > > And so we don't need the lock here. > I was thinking hotplug can get in the way, but we are inside a {get,put}_online_cpus block. I'll remove that. Thanks, - Juri -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 12-01-16, 12:08, Juri Lelli wrote: > I currently don't have any branch fetched by Fengguang's bot; I'll see > how to start doing that. In the meantime I'll try to setup an x86 box > and run some more tests. Perhaps, just create a new tree (that you always want to be tested by the Bot) and push your branch there. And then ask Fengguang ((In)formal email to: fengguang.wu@intel.com) to add your tree. He is very fast :) > I was thinking hotplug can get in the way, but we are inside a > {get,put}_online_cpus block. I'll remove that. Exactly.
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index 63d6efb..98adbc2 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -1585,6 +1585,7 @@ EXPORT_SYMBOL(cpufreq_generic_suspend); void cpufreq_suspend(void) { struct cpufreq_policy *policy; + unsigned long flags; if (!cpufreq_driver) return; @@ -1594,6 +1595,7 @@ void cpufreq_suspend(void) pr_debug("%s: Suspending Governors\n", __func__); + read_lock_irqsave(&cpufreq_driver_lock, flags); for_each_active_policy(policy) { if (__cpufreq_governor(policy, CPUFREQ_GOV_STOP)) pr_err("%s: Failed to stop governor for policy: %p\n", @@ -1603,6 +1605,7 @@ void cpufreq_suspend(void) pr_err("%s: Failed to suspend driver: %p\n", __func__, policy); } + read_unlock_irqrestore(&cpufreq_driver_lock, flags); suspend: cpufreq_suspended = true; @@ -1617,6 +1620,7 @@ suspend: void cpufreq_resume(void) { struct cpufreq_policy *policy; + unsigned long flags; if (!cpufreq_driver) return; @@ -1628,6 +1632,7 @@ void cpufreq_resume(void) pr_debug("%s: Resuming Governors\n", __func__); + read_lock_irqsave(&cpufreq_driver_lock, flags); for_each_active_policy(policy) { if (cpufreq_driver->resume && cpufreq_driver->resume(policy)) pr_err("%s: Failed to resume driver: %p\n", __func__, @@ -1637,6 +1642,7 @@ void cpufreq_resume(void) pr_err("%s: Failed to start governor for policy: %p\n", __func__, policy); } + read_unlock_irqrestore(&cpufreq_driver_lock, flags); /* * schedule call cpufreq_update_policy() for first-online CPU, as that @@ -2287,7 +2293,9 @@ static int cpufreq_boost_set_sw(int state) struct cpufreq_frequency_table *freq_table; struct cpufreq_policy *policy; int ret = -EINVAL; + unsigned long flags; + read_lock_irqsave(&cpufreq_driver_lock, flags); for_each_active_policy(policy) { freq_table = cpufreq_frequency_get_table(policy->cpu); if (freq_table) { @@ -2302,6 +2310,7 @@ static int cpufreq_boost_set_sw(int state) __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS); } } + read_unlock_irqrestore(&cpufreq_driver_lock, flags); return ret; } @@ -2432,14 +2441,16 @@ int cpufreq_register_driver(struct cpufreq_driver *driver_data) if (ret) goto err_boost_unreg; - lockdep_assert_held(&cpufreq_driver_lock); + read_lock_irqsave(&cpufreq_driver_lock, flags); if (!(cpufreq_driver->flags & CPUFREQ_STICKY) && list_empty(&cpufreq_policy_list)) { /* if all ->init() calls failed, unregister */ pr_debug("%s: No CPU initialized for driver %s\n", __func__, driver_data->name); + read_unlock_irqrestore(&cpufreq_driver_lock, flags); goto err_if_unreg; } + read_unlock_irqrestore(&cpufreq_driver_lock, flags); register_hotcpu_notifier(&cpufreq_cpu_notifier); pr_debug("driver %s up and running\n", driver_data->name);
Commit highlights paths where we access cpufreq_policy_list without holding cpufreq_driver_lock; one example being the following: [ 8.245779] ------------[ cut here ]------------ [ 8.305977] WARNING: CPU: 2 PID: 1 at kernel/drivers/cpufreq/cpufreq.c:2447 cpufreq_register_driver+0xfd/0x120() [ 8.438611] Modules linked in: [ 8.493751] CPU: 2 PID: 1 Comm: swapper/0 Not tainted 4.4.0-rc4+ #369 [ 8.561039] Hardware name: ARM-Versatile Express [ 8.622765] [<c0014215>] (unwind_backtrace) from [<c0010e25>] (show_stack+0x11/0x14) [ 8.629651] atkbd serio0: keyboard reset failed on 1c060000.kmi [ 8.810905] [<c0010e25>] (show_stack) from [<c02ece7d>] (dump_stack+0x55/0x78) [ 8.935122] [<c02ece7d>] (dump_stack) from [<c00202cd>] (warn_slowpath_common+0x59/0x84) [ 9.067097] [<c00202cd>] (warn_slowpath_common) from [<c002030f>] (warn_slowpath_null+0x17/0x1c) [ 9.204101] [<c002030f>] (warn_slowpath_null) from [<c03ba329>] (cpufreq_register_driver+0xfd/0x120) [ 9.209603] usb 1-1.2: new high-speed USB device number 3 using isp1760 [ 9.419507] [<c03ba329>] (cpufreq_register_driver) from [<c03bc481>] (bL_cpufreq_register+0x49/0x98) [ 9.560548] [<c03bc481>] (bL_cpufreq_register) from [<c0342517>] (platform_drv_probe+0x3b/0x6c) [ 9.573806] usb-storage 1-1.2:1.0: USB Mass Storage device detected [ 9.575468] scsi host0: usb-storage 1-1.2:1.0 [ 9.855845] [<c0342517>] (platform_drv_probe) from [<c03412e7>] (driver_probe_device+0x153/0x1bc) [ 10.006137] [<c03412e7>] (driver_probe_device) from [<c03413a7>] (__driver_attach+0x57/0x58) [ 10.009576] atkbd serio1: keyboard reset failed on 1c070000.kmi [ 10.237057] [<c03413a7>] (__driver_attach) from [<c0340199>] (bus_for_each_dev+0x2d/0x4c) [ 10.387824] [<c0340199>] (bus_for_each_dev) from [<c0340bd7>] (bus_add_driver+0xa3/0x14c) [ 10.539200] [<c0340bd7>] (bus_add_driver) from [<c0341bff>] (driver_register+0x3b/0x88) [ 10.691023] [<c0341bff>] (driver_register) from [<c0009613>] (do_one_initcall+0x5b/0x150) [ 10.703809] scsi 0:0:0:0: Direct-Access General USB Flash Disk 1.0 PQ: 0 ANSI: 2 [ 10.713081] sd 0:0:0:0: [sda] 7831552 512-byte logical blocks: (4.00 GB/3.73 GiB) [ 10.713973] sd 0:0:0:0: [sda] Write Protect is off [ 10.713984] sd 0:0:0:0: [sda] Mode Sense: 03 00 00 00 [ 10.730783] sd 0:0:0:0: [sda] No Caching mode page found [ 10.730814] sd 0:0:0:0: [sda] Assuming drive cache: write through [ 10.779815] sda: sda1 sda2 [ 10.823590] sd 0:0:0:0: [sda] Attached SCSI removable disk [ 11.581894] [<c0009613>] (do_one_initcall) from [<c0734b45>] (kernel_init_freeable+0x18d/0x22c) [ 11.720454] [<c0734b45>] (kernel_init_freeable) from [<c04f45f9>] (kernel_init+0xd/0xa4) [ 11.857340] [<c04f45f9>] (kernel_init) from [<c000dfb9>] (ret_from_fork+0x11/0x38) [ 11.993082] ---[ end trace 62ff5522fb3f41dd ]--- Fix this, and others, with proper locking of cpufreq_driver_lock. Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> Cc: Viresh Kumar <viresh.kumar@linaro.org> Signed-off-by: Juri Lelli <juri.lelli@arm.com> --- drivers/cpufreq/cpufreq.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-)