@@ -29,7 +29,7 @@
*/
static LIST_HEAD(dev_opp_list);
/* Lock to allow exclusive modification to the device and opp lists */
-static DEFINE_MUTEX(dev_opp_list_lock);
+DEFINE_MUTEX(dev_opp_list_lock);
#define opp_rcu_lockdep_assert() \
do { \
@@ -127,12 +127,12 @@ int dev_pm_opp_set_sharing_cpus(struct device *cpu_dev, cpumask_var_t cpumask)
struct device *dev;
int cpu, ret = 0;
- rcu_read_lock();
+ mutex_lock(&dev_opp_list_lock);
dev_opp = _find_device_opp(cpu_dev);
if (IS_ERR(dev_opp)) {
ret = -EINVAL;
- goto out_rcu_read_unlock;
+ goto unlock;
}
for_each_cpu(cpu, cpumask) {
@@ -153,8 +153,8 @@ int dev_pm_opp_set_sharing_cpus(struct device *cpu_dev, cpumask_var_t cpumask)
continue;
}
}
-out_rcu_read_unlock:
- rcu_read_unlock();
+unlock:
+ mutex_unlock(&dev_opp_list_lock);
return ret;
}
@@ -21,6 +21,9 @@
#include <linux/rculist.h>
#include <linux/rcupdate.h>
+/* Lock to allow exclusive modification to the device and opp lists */
+extern struct mutex dev_opp_list_lock;
+
/*
* Internal data structure organization with the OPP layer library is as
* follows:
dev_opp_list_lock is used everywhere to protect device and OPP lists, but dev_pm_opp_set_sharing_cpus() is missed somehow. And instead we used rcu-lock, which wouldn't help here as we are adding a new list_dev. This also fixes a problem where we have called kzalloc(..., GFP_KERNEL) from within rcu-lock, which isn't allowed as kzalloc can sleep when called with GFP_KERNEL. With CONFIG_DEBUG_ATOMIC_SLEEP set, we get following lockdep-splat: include/linux/rcupdate.h:578 Illegal context switch in RCU read-side critical section! other info that might help us debug this: rcu_scheduler_active = 1, debug_locks = 0 5 locks held by swapper/0/1: #0: (&dev->mutex){......}, at: [<c02f68f4>] __driver_attach+0x48/0x98 #1: (&dev->mutex){......}, at: [<c02f6904>] __driver_attach+0x58/0x98 #2: (cpu_hotplug.lock){++++++}, at: [<c00249d0>] get_online_cpus+0x40/0xb0 #3: (subsys mutex#5){+.+.+.}, at: [<c02f4f8c>] subsys_interface_register+0x44/0xdc #4: (rcu_read_lock){......}, at: [<c0305c80>] dev_pm_opp_set_sharing_cpus+0x0/0x1e4 stack backtrace: CPU: 1 PID: 1 Comm: swapper/0 Tainted: G W 4.3.0-rc7-00047-g81f5932958a8 #59 Hardware name: SAMSUNG EXYNOS (Flattened Device Tree) [<c0016874>] (unwind_backtrace) from [<c001355c>] (show_stack+0x10/0x14) [<c001355c>] (show_stack) from [<c022553c>] (dump_stack+0x94/0xbc) [<c022553c>] (dump_stack) from [<c004904c>] (___might_sleep+0x24c/0x298) [<c004904c>] (___might_sleep) from [<c00f07e4>] (kmem_cache_alloc+0xe8/0x164) [<c00f07e4>] (kmem_cache_alloc) from [<c0305354>] (_add_list_dev+0x30/0x58) [<c0305354>] (_add_list_dev) from [<c0305d50>] (dev_pm_opp_set_sharing_cpus+0xd0/0x1e4) [<c0305d50>] (dev_pm_opp_set_sharing_cpus) from [<c040eda4>] (cpufreq_init+0x4cc/0x62c) [<c040eda4>] (cpufreq_init) from [<c040a964>] (cpufreq_online+0xbc/0x73c) [<c040a964>] (cpufreq_online) from [<c02f4fe0>] (subsys_interface_register+0x98/0xdc) [<c02f4fe0>] (subsys_interface_register) from [<c040a640>] (cpufreq_register_driver+0x110/0x17c) [<c040a640>] (cpufreq_register_driver) from [<c040ef64>] (dt_cpufreq_probe+0x60/0x8c) [<c040ef64>] (dt_cpufreq_probe) from [<c02f8084>] (platform_drv_probe+0x44/0xa4) [<c02f8084>] (platform_drv_probe) from [<c02f67c0>] (driver_probe_device+0x208/0x2f4) [<c02f67c0>] (driver_probe_device) from [<c02f6940>] (__driver_attach+0x94/0x98) [<c02f6940>] (__driver_attach) from [<c02f4c1c>] (bus_for_each_dev+0x68/0x9c) Cc: 4.3 <stable@vger.kernel.org> # 4.3 Reported-by: Michael Turquette <mturquette@baylibre.com> Reviewed-by: Stephen Boyd <sboyd@codeaurora.org> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> --- drivers/base/power/opp/core.c | 2 +- drivers/base/power/opp/cpu.c | 8 ++++---- drivers/base/power/opp/opp.h | 3 +++ 3 files changed, 8 insertions(+), 5 deletions(-) -- 2.6.2.198.g614a2ac -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/