From 87b4115db0239865bc812f61704bb1f43e2439b6 Mon Sep 17 00:00:00 2001 From: Viresh Kumar Date: Thu, 5 Nov 2015 14:21:19 +0530 Subject: [PATCH] PM / OPP: Protect updates to list_dev with mutex 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: [] __driver_attach+0x48/0x98 #1: (&dev->mutex){......}, at: [] __driver_attach+0x58/0x98 #2: (cpu_hotplug.lock){++++++}, at: [] get_online_cpus+0x40/0xb0 #3: (subsys mutex#5){+.+.+.}, at: [] subsys_interface_register+0x44/0xdc #4: (rcu_read_lock){......}, at: [] 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) [] (unwind_backtrace) from [] (show_stack+0x10/0x14) [] (show_stack) from [] (dump_stack+0x94/0xbc) [] (dump_stack) from [] (___might_sleep+0x24c/0x298) [] (___might_sleep) from [] (kmem_cache_alloc+0xe8/0x164) [] (kmem_cache_alloc) from [] (_add_list_dev+0x30/0x58) [] (_add_list_dev) from [] (dev_pm_opp_set_sharing_cpus+0xd0/0x1e4) [] (dev_pm_opp_set_sharing_cpus) from [] (cpufreq_init+0x4cc/0x62c) [] (cpufreq_init) from [] (cpufreq_online+0xbc/0x73c) [] (cpufreq_online) from [] (subsys_interface_register+0x98/0xdc) [] (subsys_interface_register) from [] (cpufreq_register_driver+0x110/0x17c) [] (cpufreq_register_driver) from [] (dt_cpufreq_probe+0x60/0x8c) [] (dt_cpufreq_probe) from [] (platform_drv_probe+0x44/0xa4) [] (platform_drv_probe) from [] (driver_probe_device+0x208/0x2f4) [] (driver_probe_device) from [] (__driver_attach+0x94/0x98) [] (__driver_attach) from [] (bus_for_each_dev+0x68/0x9c) Reported-by: Michael Turquette Reviewed-by: Stephen Boyd Signed-off-by: Viresh Kumar Cc: 4.3 # 4.3 Signed-off-by: Rafael J. Wysocki --- 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(-) diff --git a/drivers/base/power/opp/core.c b/drivers/base/power/opp/core.c index ccf2c91aedff..252706d6f60b 100644 --- a/drivers/base/power/opp/core.c +++ b/drivers/base/power/opp/core.c @@ -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 { \ diff --git a/drivers/base/power/opp/cpu.c b/drivers/base/power/opp/cpu.c index 2139c9d4c447..7b445e88a0d5 100644 --- a/drivers/base/power/opp/cpu.c +++ b/drivers/base/power/opp/cpu.c @@ -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; } diff --git a/drivers/base/power/opp/opp.h b/drivers/base/power/opp/opp.h index dcb38f78dae4..7366b2aa8997 100644 --- a/drivers/base/power/opp/opp.h +++ b/drivers/base/power/opp/opp.h @@ -21,6 +21,9 @@ #include #include +/* 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: -- 2.45.2