Messages in this thread | | | Date | Wed, 12 May 2010 16:08:37 +0800 | From | Américo Wang <> | Subject | Re: [PATCH] [CPUFREQ] fix race condition in store_scaling_governor |
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On Tue, May 11, 2010 at 04:20:41PM +0200, Andrej Gelenberg wrote: >Wrap store_scaling_governor with mutex lock cpufreq_governor_mutex. >Fix kernel panic if switch scaling governor very fast. >Bug in bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=15948 > >Signed-off-by: Andrej Gelenberg <andrej.gelenberg@udo.edu> >--- > drivers/cpufreq/cpufreq.c | 16 +++++++++++----- > 1 files changed, 11 insertions(+), 5 deletions(-) > >diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c >index 75d293e..6ba42f9 100644 >--- a/drivers/cpufreq/cpufreq.c >+++ b/drivers/cpufreq/cpufreq.c >@@ -403,8 +403,6 @@ static int cpufreq_parse_governor(char >*str_governor, unsigned int *policy, > } else if (cpufreq_driver->target) { > struct cpufreq_governor *t; > >- mutex_lock(&cpufreq_governor_mutex); >- > t = __find_governor(str_governor); > > if (t == NULL) { >@@ -429,8 +427,6 @@ static int cpufreq_parse_governor(char >*str_governor, unsigned int *policy, > *governor = t; > err = 0; > } >- >- mutex_unlock(&cpufreq_governor_mutex); > } > out: > return err; >@@ -521,7 +517,7 @@ static ssize_t show_scaling_governor(struct >cpufreq_policy *policy, char *buf) > /** > * store_scaling_governor - store policy for the specified CPU > */ >-static ssize_t store_scaling_governor(struct cpufreq_policy *policy, >+static ssize_t _store_scaling_governor(struct cpufreq_policy *policy, > const char *buf, size_t count) > { > unsigned int ret = -EINVAL; >@@ -553,6 +549,16 @@ static ssize_t store_scaling_governor(struct >cpufreq_policy *policy, > return count; > } > >+static ssize_t store_scaling_governor(struct cpufreq_policy *policy, >+ const char *buf, size_t count) >+{ >+ ssize_t ret; >+ mutex_lock(&cpufreq_governor_mutex); >+ ret = _store_scaling_governor(policy, buf, count); >+ mutex_unlock(&cpufreq_governor_mutex); >+ return ret; >+} >+
Sorry, I don't get it, cpufreq_governor_mutex is used to protect cpufreq_governor_list. What is the point of moving it up? Can you explain what the race condition is?
Thanks!
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