From 5025d628c8659fbf939f929107bf76db81dcdfff Mon Sep 17 00:00:00 2001 From: Li Zhong Date: Wed, 21 Aug 2013 01:31:08 +0200 Subject: [PATCH] cpufreq: fix bad unlock balance on !CONFIG_SMP This patch tries to fix lockdep complaint attached below. It seems that we should always read acquire the cpufreq_rwsem, whether CONFIG_SMP is enabled or not. And CONFIG_HOTPLUG_CPU depends on CONFIG_SMP, so it seems we don't need CONFIG_SMP for the code enabled by CONFIG_HOTPLUG_CPU. [ 0.504191] ===================================== [ 0.504627] [ BUG: bad unlock balance detected! ] [ 0.504627] 3.11.0-rc6-next-20130819 #1 Not tainted [ 0.504627] ------------------------------------- [ 0.504627] swapper/1 is trying to release lock (cpufreq_rwsem) at: [ 0.504627] [] cpufreq_add_dev+0x13a/0x3e0 [ 0.504627] but there are no more locks to release! [ 0.504627] [ 0.504627] other info that might help us debug this: [ 0.504627] 1 lock held by swapper/1: [ 0.504627] #0: (subsys mutex#4){+.+.+.}, at: [] subsys_interface_register+0x4f/0xe0 [ 0.504627] [ 0.504627] stack backtrace: [ 0.504627] CPU: 0 PID: 1 Comm: swapper Not tainted 3.11.0-rc6-next-20130819 #1 [ 0.504627] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2007 [ 0.504627] ffffffff813d927a ffff88007f847c98 ffffffff814c062b ffff88007f847cc8 [ 0.504627] ffffffff81098bce ffff88007f847cf8 ffffffff81aadc30 ffffffff813d927a [ 0.504627] 00000000ffffffff ffff88007f847d68 ffffffff8109d0be 0000000000000006 [ 0.504627] Call Trace: [ 0.504627] [] ? cpufreq_add_dev+0x13a/0x3e0 [ 0.504627] [] dump_stack+0x19/0x1b [ 0.504627] [] print_unlock_imbalance_bug+0xfe/0x110 [ 0.504627] [] ? cpufreq_add_dev+0x13a/0x3e0 [ 0.504627] [] lock_release_non_nested+0x1ee/0x310 [ 0.504627] [] ? mark_held_locks+0xae/0x120 [ 0.504627] [] ? kfree+0xcb/0x1d0 [ 0.504627] [] ? cpufreq_policy_free+0x4a/0x60 [ 0.504627] [] ? cpufreq_add_dev+0x13a/0x3e0 [ 0.504627] [] lock_release+0xc4/0x250 [ 0.504627] [] up_read+0x23/0x40 [ 0.504627] [] cpufreq_add_dev+0x13a/0x3e0 [ 0.504627] [] subsys_interface_register+0x99/0xe0 [ 0.504627] [] ? cpufreq_gov_dbs_init+0x12/0x12 [ 0.504627] [] cpufreq_register_driver+0x9d/0x1d0 [ 0.504627] [] ? cpufreq_gov_dbs_init+0x12/0x12 [ 0.504627] [] acpi_cpufreq_init+0xfe/0x1f8 [ 0.504627] [] do_one_initcall+0xda/0x180 [ 0.504627] [] kernel_init_freeable+0x12c/0x1bb [ 0.504627] [] ? do_early_param+0x8c/0x8c [ 0.504627] [] ? rest_init+0x140/0x140 [ 0.504627] [] kernel_init+0xe/0xf0 [ 0.504627] [] ret_from_fork+0x7a/0xb0 [ 0.504627] [] ? rest_init+0x140/0x140 Signed-off-by: Li Zhong Acked-and-tested-by: Viresh Kumar Signed-off-by: Rafael J. Wysocki --- drivers/cpufreq/cpufreq.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index 81ceea6ed630..5c75e3147a60 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -978,6 +978,7 @@ static int __cpufreq_add_dev(struct device *dev, struct subsys_interface *sif, cpufreq_cpu_put(policy); return 0; } +#endif if (!down_read_trylock(&cpufreq_rwsem)) return 0; @@ -994,7 +995,6 @@ static int __cpufreq_add_dev(struct device *dev, struct subsys_interface *sif, } } read_unlock_irqrestore(&cpufreq_driver_lock, flags); -#endif #endif if (frozen)