| Message ID | 1452533760-13787-10-git-send-email-juri.lelli@arm.com (mailing list archive) |
|---|---|
| State | RFC |
| Headers | show |
On 11-01-16, 17:35, Juri Lelli wrote: > show_scaling_available_governors iterates through cpufreq_governor_list > without holding cpufreq_governor_mutex; this generates the following > warning: > > [ 700.910381] ------------[ cut here ]------------ > [ 700.924282] WARNING: CPU: 2 PID: 1756 at kernel/drivers/cpufreq/cpufreq.c:700 show_scaling_available_governors+0x6f/0xb8() > [ 700.965473] Modules linked in: > [ 700.974637] CPU: 2 PID: 1756 Comm: cat Tainted: G W 4.4.0-rc2+ #299 > [ 700.996813] Hardware name: ARM-Versatile Express > [ 701.010674] [<c0014215>] (unwind_backtrace) from [<c0010e25>] (show_stack+0x11/0x14) > [ 701.033905] [<c0010e25>] (show_stack) from [<c02eca5d>] (dump_stack+0x55/0x78) > [ 701.055561] [<c02eca5d>] (dump_stack) from [<c00202cd>] (warn_slowpath_common+0x59/0x84) > [ 701.079839] [<c00202cd>] (warn_slowpath_common) from [<c002030f>] (warn_slowpath_null+0x17/0x1c) > [ 701.106182] [<c002030f>] (warn_slowpath_null) from [<c03b7bef>] (show_scaling_available_governors+0x6f/0xb8) > [ 701.135656] [<c03b7bef>] (show_scaling_available_governors) from [<c03b7dc3>] (show+0x27/0x38) > [ 701.161488] [<c03b7dc3>] (show) from [<c015469f>] (sysfs_kf_seq_show+0x5f/0xa0) > [ 701.183409] [<c015469f>] (sysfs_kf_seq_show) from [<c01536a7>] (kernfs_seq_show+0x1b/0x1c) > [ 701.208188] [<c01536a7>] (kernfs_seq_show) from [<c011a6d5>] (seq_read+0x129/0x33c) > [ 701.231161] [<c011a6d5>] (seq_read) from [<c00ff7c7>] (__vfs_read+0x1b/0x84) > [ 701.252300] [<c00ff7c7>] (__vfs_read) from [<c010000f>] (vfs_read+0x5f/0xb0) > [ 701.273436] [<c010000f>] (vfs_read) from [<c0100099>] (SyS_read+0x39/0x68) > [ 701.294049] [<c0100099>] (SyS_read) from [<c000df21>] (ret_fast_syscall+0x1/0x1a) > [ 701.316484] ---[ end trace 5dd15744a4da127c ]--- FWIW, I would suggest you to use cpufreq-dt for Juno instead of arm_bL. I have asked Sudeep to do it earlier, but perhaps he was busy. > Fix this by locking cpufreq_governor_mutex before for_each_governor(). > > 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 | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c > index d065435..d91fdb8 100644 > --- a/drivers/cpufreq/cpufreq.c > +++ b/drivers/cpufreq/cpufreq.c > @@ -694,7 +694,7 @@ static ssize_t show_scaling_available_governors(struct cpufreq_policy *policy, > goto out; > } > > - lockdep_assert_held(&cpufreq_governor_mutex); > + mutex_lock(&cpufreq_governor_mutex); > for_each_governor(t) { > if (i >= (ssize_t) ((PAGE_SIZE / sizeof(char)) > - (CPUFREQ_NAME_LEN + 2))) > @@ -702,6 +702,7 @@ static ssize_t show_scaling_available_governors(struct cpufreq_policy *policy, > i += scnprintf(&buf[i], CPUFREQ_NAME_PLEN, "%s ", t->name); > } > out: > + mutex_unlock(&cpufreq_governor_mutex); > i += sprintf(&buf[i], "\n"); > return i; > } Just move this patch before before the patch that added the lockdep-assert and we wouldn't be required to add the lockdep_assert_held() in the first place.
Hi, On 12/01/16 15:43, Viresh Kumar wrote: > On 11-01-16, 17:35, Juri Lelli wrote: > > show_scaling_available_governors iterates through cpufreq_governor_list > > without holding cpufreq_governor_mutex; this generates the following > > warning: > > > > [ 700.910381] ------------[ cut here ]------------ > > [ 700.924282] WARNING: CPU: 2 PID: 1756 at kernel/drivers/cpufreq/cpufreq.c:700 show_scaling_available_governors+0x6f/0xb8() > > [ 700.965473] Modules linked in: > > [ 700.974637] CPU: 2 PID: 1756 Comm: cat Tainted: G W 4.4.0-rc2+ #299 > > [ 700.996813] Hardware name: ARM-Versatile Express > > [ 701.010674] [<c0014215>] (unwind_backtrace) from [<c0010e25>] (show_stack+0x11/0x14) > > [ 701.033905] [<c0010e25>] (show_stack) from [<c02eca5d>] (dump_stack+0x55/0x78) > > [ 701.055561] [<c02eca5d>] (dump_stack) from [<c00202cd>] (warn_slowpath_common+0x59/0x84) > > [ 701.079839] [<c00202cd>] (warn_slowpath_common) from [<c002030f>] (warn_slowpath_null+0x17/0x1c) > > [ 701.106182] [<c002030f>] (warn_slowpath_null) from [<c03b7bef>] (show_scaling_available_governors+0x6f/0xb8) > > [ 701.135656] [<c03b7bef>] (show_scaling_available_governors) from [<c03b7dc3>] (show+0x27/0x38) > > [ 701.161488] [<c03b7dc3>] (show) from [<c015469f>] (sysfs_kf_seq_show+0x5f/0xa0) > > [ 701.183409] [<c015469f>] (sysfs_kf_seq_show) from [<c01536a7>] (kernfs_seq_show+0x1b/0x1c) > > [ 701.208188] [<c01536a7>] (kernfs_seq_show) from [<c011a6d5>] (seq_read+0x129/0x33c) > > [ 701.231161] [<c011a6d5>] (seq_read) from [<c00ff7c7>] (__vfs_read+0x1b/0x84) > > [ 701.252300] [<c00ff7c7>] (__vfs_read) from [<c010000f>] (vfs_read+0x5f/0xb0) > > [ 701.273436] [<c010000f>] (vfs_read) from [<c0100099>] (SyS_read+0x39/0x68) > > [ 701.294049] [<c0100099>] (SyS_read) from [<c000df21>] (ret_fast_syscall+0x1/0x1a) > > [ 701.316484] ---[ end trace 5dd15744a4da127c ]--- > > FWIW, I would suggest you to use cpufreq-dt for Juno instead of > arm_bL. I have asked Sudeep to do it earlier, but perhaps he was busy. > I couldn't really relate this comment with this patch or the backtrace. Can you please clarify why you are referring to switching to use cpufreq-dt here? > > Fix this by locking cpufreq_governor_mutex before for_each_governor(). > > > > 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 | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c > > index d065435..d91fdb8 100644 > > --- a/drivers/cpufreq/cpufreq.c > > +++ b/drivers/cpufreq/cpufreq.c > > @@ -694,7 +694,7 @@ static ssize_t show_scaling_available_governors(struct cpufreq_policy *policy, > > goto out; > > } > > > > - lockdep_assert_held(&cpufreq_governor_mutex); > > + mutex_lock(&cpufreq_governor_mutex); > > for_each_governor(t) { > > if (i >= (ssize_t) ((PAGE_SIZE / sizeof(char)) > > - (CPUFREQ_NAME_LEN + 2))) > > @@ -702,6 +702,7 @@ static ssize_t show_scaling_available_governors(struct cpufreq_policy *policy, > > i += scnprintf(&buf[i], CPUFREQ_NAME_PLEN, "%s ", t->name); > > } > > out: > > + mutex_unlock(&cpufreq_governor_mutex); > > i += sprintf(&buf[i], "\n"); > > return i; > > } > > Just move this patch before before the patch that added the > lockdep-assert and we wouldn't be required to add the > lockdep_assert_held() in the first place. > Yep. As said, I just wanted to try to highlight possible problems with this RFC. 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 13-01-16, 10:25, Juri Lelli wrote: > I couldn't really relate this comment with this patch or the backtrace. > Can you please clarify why you are referring to switching to use > cpufreq-dt here? Yeah, sorry about that. One of your previous patches had backtrace mentioning bL and so I wanted to mention that thing to you. But by that time, I moved to the new patch and thought of just adding the point before forgetting it completely.
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index d065435..d91fdb8 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -694,7 +694,7 @@ static ssize_t show_scaling_available_governors(struct cpufreq_policy *policy, goto out; } - lockdep_assert_held(&cpufreq_governor_mutex); + mutex_lock(&cpufreq_governor_mutex); for_each_governor(t) { if (i >= (ssize_t) ((PAGE_SIZE / sizeof(char)) - (CPUFREQ_NAME_LEN + 2))) @@ -702,6 +702,7 @@ static ssize_t show_scaling_available_governors(struct cpufreq_policy *policy, i += scnprintf(&buf[i], CPUFREQ_NAME_PLEN, "%s ", t->name); } out: + mutex_unlock(&cpufreq_governor_mutex); i += sprintf(&buf[i], "\n"); return i; }
show_scaling_available_governors iterates through cpufreq_governor_list without holding cpufreq_governor_mutex; this generates the following warning: [ 700.910381] ------------[ cut here ]------------ [ 700.924282] WARNING: CPU: 2 PID: 1756 at kernel/drivers/cpufreq/cpufreq.c:700 show_scaling_available_governors+0x6f/0xb8() [ 700.965473] Modules linked in: [ 700.974637] CPU: 2 PID: 1756 Comm: cat Tainted: G W 4.4.0-rc2+ #299 [ 700.996813] Hardware name: ARM-Versatile Express [ 701.010674] [<c0014215>] (unwind_backtrace) from [<c0010e25>] (show_stack+0x11/0x14) [ 701.033905] [<c0010e25>] (show_stack) from [<c02eca5d>] (dump_stack+0x55/0x78) [ 701.055561] [<c02eca5d>] (dump_stack) from [<c00202cd>] (warn_slowpath_common+0x59/0x84) [ 701.079839] [<c00202cd>] (warn_slowpath_common) from [<c002030f>] (warn_slowpath_null+0x17/0x1c) [ 701.106182] [<c002030f>] (warn_slowpath_null) from [<c03b7bef>] (show_scaling_available_governors+0x6f/0xb8) [ 701.135656] [<c03b7bef>] (show_scaling_available_governors) from [<c03b7dc3>] (show+0x27/0x38) [ 701.161488] [<c03b7dc3>] (show) from [<c015469f>] (sysfs_kf_seq_show+0x5f/0xa0) [ 701.183409] [<c015469f>] (sysfs_kf_seq_show) from [<c01536a7>] (kernfs_seq_show+0x1b/0x1c) [ 701.208188] [<c01536a7>] (kernfs_seq_show) from [<c011a6d5>] (seq_read+0x129/0x33c) [ 701.231161] [<c011a6d5>] (seq_read) from [<c00ff7c7>] (__vfs_read+0x1b/0x84) [ 701.252300] [<c00ff7c7>] (__vfs_read) from [<c010000f>] (vfs_read+0x5f/0xb0) [ 701.273436] [<c010000f>] (vfs_read) from [<c0100099>] (SyS_read+0x39/0x68) [ 701.294049] [<c0100099>] (SyS_read) from [<c000df21>] (ret_fast_syscall+0x1/0x1a) [ 701.316484] ---[ end trace 5dd15744a4da127c ]--- Fix this by locking cpufreq_governor_mutex before for_each_governor(). 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 | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)