Messages in this thread | | | Date | Tue, 12 Jan 2016 15:43:15 +0530 | From | Viresh Kumar <> | Subject | Re: [RFC PATCH 09/19] cpufreq: fix warning for show_scaling_available_governors unlocked access to cpufreq_governor_list |
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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.
-- viresh
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