From a0982afa0992a9b9ecfe610d6a31fc05bb15a05a Mon Sep 17 00:00:00 2001 From: Seyediman Seyedarab Date: Mon, 12 May 2025 21:57:26 -0400 Subject: [PATCH] cpufreq: drop redundant cpus_read_lock() from store_local_boost() Lockdep reports a possible circular locking dependency [1] when cpu_hotplug_lock is acquired inside store_local_boost(), after policy->rwsem has already been taken by store(). However, the boost update is strictly per-policy and does not access shared state or iterate over all policies. Since policy->rwsem is already held, this is enough to serialize against concurrent topology changes for the current policy. Remove the cpus_read_lock() to resolve the lockdep warning and avoid unnecessary locking. [1] ====================================================== WARNING: possible circular locking dependency detected 6.15.0-rc6-debug-gb01fc4eca73c #1 Not tainted ------------------------------------------------------ power-profiles-/588 is trying to acquire lock: ffffffffb3a7d910 (cpu_hotplug_lock){++++}-{0:0}, at: store_local_boost+0x56/0xd0 but task is already holding lock: ffff8b6e5a12c380 (&policy->rwsem){++++}-{4:4}, at: store+0x37/0x90 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&policy->rwsem){++++}-{4:4}: down_write+0x29/0xb0 cpufreq_online+0x7e8/0xa40 cpufreq_add_dev+0x82/0xa0 subsys_interface_register+0x148/0x160 cpufreq_register_driver+0x15d/0x260 amd_pstate_register_driver+0x36/0x90 amd_pstate_init+0x1e7/0x270 do_one_initcall+0x68/0x2b0 kernel_init_freeable+0x231/0x270 kernel_init+0x15/0x130 ret_from_fork+0x2c/0x50 ret_from_fork_asm+0x11/0x20 -> #1 (subsys mutex#3){+.+.}-{4:4}: __mutex_lock+0xc2/0x930 subsys_interface_register+0x7f/0x160 cpufreq_register_driver+0x15d/0x260 amd_pstate_register_driver+0x36/0x90 amd_pstate_init+0x1e7/0x270 do_one_initcall+0x68/0x2b0 kernel_init_freeable+0x231/0x270 kernel_init+0x15/0x130 ret_from_fork+0x2c/0x50 ret_from_fork_asm+0x11/0x20 -> #0 (cpu_hotplug_lock){++++}-{0:0}: __lock_acquire+0x10ed/0x1850 lock_acquire.part.0+0x69/0x1b0 cpus_read_lock+0x2a/0xc0 store_local_boost+0x56/0xd0 store+0x50/0x90 kernfs_fop_write_iter+0x132/0x200 vfs_write+0x2b3/0x590 ksys_write+0x74/0xf0 do_syscall_64+0xbb/0x1d0 entry_SYSCALL_64_after_hwframe+0x56/0x5e Signed-off-by: Seyediman Seyedarab Link: https://patch.msgid.link/20250513015726.1497-1-ImanDevel@gmail.com Signed-off-by: Rafael J. Wysocki --- drivers/cpufreq/cpufreq.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index be727da0be4d..cb475ac5b618 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -622,10 +622,7 @@ static ssize_t store_local_boost(struct cpufreq_policy *policy, if (!policy->boost_supported) return -EINVAL; - cpus_read_lock(); ret = policy_set_boost(policy, enable); - cpus_read_unlock(); - if (!ret) return count;