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Date: Sun, 16 Oct 2011 18:56:47 +0800
From: Yong Zhang <yong.zhang0@...il.com>
To: linux-kernel@...r.kernel.org
Cc: linux-rt-users@...r.kernel.org, tglx@...utronix.de
Subject: [RFC] [PATCH -rt 5/5] cpufreq: get rid of get_online_cpus()/put_online_cpus()
Fix below false positive (seems this is not a real deadlock scenario)
lockdep warning:
=======================================================
[ INFO: possible circular locking dependency detected ]
3.0.6-rt18-00293-g6f698ae-dirty #24
-------------------------------------------------------
bash/1709 is trying to acquire lock:
(s_active#103){++++.+}, at: [<c02ab4a3>] sysfs_addrm_finish+0x33/0x60
but task is already holding lock:
(cpu_hotplug.lock){+.+.+.}, at: [<c0150530>] cpu_hotplug_begin+0x20/0x50
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 (cpu_hotplug.lock){+.+.+.}:
[<c018ba31>] validate_chain.clone.20+0x701/0x810
[<c018e1c4>] __lock_acquire+0x3b4/0x8d0
[<c018eda8>] lock_acquire+0x88/0x1b0
[<c0736b48>] _mutex_lock+0x38/0x50
[<c01506a1>] get_online_cpus+0x31/0x50
[<c05ea533>] cpufreq_add_dev_interface+0x103/0x270
[<c05ea9ac>] cpufreq_add_dev+0x30c/0x410
[<c0524aa1>] sysdev_driver_register+0xb1/0x140
[<c05e988e>] cpufreq_register_driver+0x8e/0x150
[<c0a25e92>] acpi_cpufreq_init+0x78/0x8b
[<c0101225>] do_one_initcall+0x35/0x170
[<c09f5852>] kernel_init+0xb8/0x14e
[<c073e742>] kernel_thread_helper+0x6/0x10
-> #1 (&(*({ do { const void *__vpp_verify = (typeof((&(cpu_policy_rwsem))))((void *)0); (void)__vpp_verify; } while (0); ({ unsigned long __ptr; __asm__ ("" : "=r"(__ptr) : "0"((typeof(*(&(cpu_policy_rwsem))) *)(&(cpu_policy_rwsem)))); (typeof((typeof(*(&(cpu_policy_rwsem))) *)(&(cpu_policy_rwsem)))) (__ptr + (((__per_cpu_offset[cpu])))); }); }))){+++++.}:
[<c018ba31>] validate_chain.clone.20+0x701/0x810
[<c018e1c4>] __lock_acquire+0x3b4/0x8d0
[<c018eda8>] lock_acquire+0x88/0x1b0
[<c0195f66>] __rt_down_read+0x36/0x60
[<c0195faf>] rt_down_read+0xf/0x20
[<c05e975f>] lock_policy_rwsem_read+0x3f/0x80
[<c05ea3f4>] show+0x34/0x70
[<c02a9fb7>] sysfs_read_file+0x87/0x130
[<c024522f>] vfs_read+0x9f/0x170
[<c0245348>] sys_read+0x48/0x80
[<c073e15f>] sysenter_do_call+0x12/0x38
-> #0 (s_active#103){++++.+}:
[<c018b2fa>] check_prev_add+0x5fa/0x630
[<c018ba31>] validate_chain.clone.20+0x701/0x810
[<c018e1c4>] __lock_acquire+0x3b4/0x8d0
[<c018eda8>] lock_acquire+0x88/0x1b0
[<c02aac85>] sysfs_deactivate+0xc5/0x120
[<c02ab4a3>] sysfs_addrm_finish+0x33/0x60
[<c02aba0a>] sysfs_remove_dir+0x6a/0x80
[<c03bab3f>] kobject_del+0xf/0x30
[<c03babbf>] kobject_release+0x5f/0x80
[<c03bbf3d>] kref_put+0x2d/0x60
[<c03baa7d>] kobject_put+0x1d/0x50
[<c05eab6e>] __cpufreq_remove_dev+0xbe/0x260
[<c07339f3>] cpufreq_cpu_callback+0x70/0x83
[<c073ac5a>] notifier_call_chain+0x7a/0xa0
[<c017a3fe>] __raw_notifier_call_chain+0x1e/0x30
[<c0150494>] __cpu_notify+0x24/0x40
[<c071b7c1>] _cpu_down+0x151/0x350
[<c071b9f0>] cpu_down+0x30/0x50
[<c071d550>] store_online+0x50/0xa7
[<c052466a>] sysdev_store+0x2a/0x40
[<c02a9ed4>] sysfs_write_file+0xa4/0x100
[<c02450c2>] vfs_write+0xa2/0x170
[<c02453c8>] sys_write+0x48/0x80
[<c073e15f>] sysenter_do_call+0x12/0x38
other info that might help us debug this:
Chain exists of:
s_active --> &(*({ do { const void *__vpp_verify = (typeof((&(cpu_policy_rwsem))))((void *)0); (void)__vpp_verify; } while (0); ({ unsigned long __ptr; __asm__ ("" : "=r"(__ptr) : "0"((typeof(*(&(cpu_policy_rwsem))) *)(&(cpu_policy_rwsem)))); (typeof((typeof(*(&(cpu_policy_rwsem))) *)(&(cpu_policy_rwsem)))) (__ptr + (((__per_cpu_offset[cpu])))); }); })) --> cpu_hotplug.lock
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(cpu_hotplug.lock);
lock(&(*({ do { const void *__vpp_verify = (typeof((&(cpu_policy_rwsem))))((void *)0); (void)__vpp_verify; } while (0); ({ unsigned long __ptr; __asm__ ("" : "=r"(__ptr) : "0"((typeof(*(&(cpu_policy_rwsem))) *)(&(cpu_policy_rwsem)))); (typeof((typeof(*(&(cpu_policy_rwsem))) *)(&(cpu_policy_rwsem)))) (__ptr + (((__per_cpu_offset[cpu])))); }); })));
lock(cpu_hotplug.lock);
lock(s_active);
*** DEADLOCK ***
5 locks held by bash/1709:
#0: (&buffer->mutex){+.+.+.}, at: [<c02a9e57>] sysfs_write_file+0x27/0x100
#1: (s_active#119){.+.+.+}, at: [<c02a9eb9>] sysfs_write_file+0x89/0x100
#2: (x86_cpu_hotplug_driver_mutex){+.+.+.}, at: [<c011dc42>] cpu_hotplug_driver_lock+0x12/0x20
#3: (cpu_add_remove_lock){+.+.+.}, at: [<c01506d2>] cpu_maps_update_begin+0x12/0x20
#4: (cpu_hotplug.lock){+.+.+.}, at: [<c0150530>] cpu_hotplug_begin+0x20/0x50
stack backtrace:
Pid: 1709, comm: bash Not tainted 3.0.6-rt18-00293-g6f698ae-dirty #24
Call Trace:
[<c0733d94>] ? printk+0x1d/0x21
[<c018a28f>] print_circular_bug+0xcf/0xe0
[<c018b2fa>] check_prev_add+0x5fa/0x630
[<c018bfd9>] ? mark_lock_irq+0xc9/0x270
[<c018ba31>] validate_chain.clone.20+0x701/0x810
[<c018e1c4>] __lock_acquire+0x3b4/0x8d0
[<c018ef24>] ? lockdep_init_map+0x54/0x4e0
[<c018eda8>] lock_acquire+0x88/0x1b0
[<c02ab4a3>] ? sysfs_addrm_finish+0x33/0x60
[<c02aac85>] sysfs_deactivate+0xc5/0x120
[<c02ab4a3>] ? sysfs_addrm_finish+0x33/0x60
[<c0234382>] ? unlock_slab_and_free_delayed.clone.25+0x92/0xc0
[<c0234382>] ? unlock_slab_and_free_delayed.clone.25+0x92/0xc0
[<c02ab4a3>] sysfs_addrm_finish+0x33/0x60
[<c02aba0a>] sysfs_remove_dir+0x6a/0x80
[<c03bab3f>] kobject_del+0xf/0x30
[<c03babbf>] kobject_release+0x5f/0x80
[<c03bab60>] ? kobject_del+0x30/0x30
[<c03bbf3d>] kref_put+0x2d/0x60
[<c03baa7d>] kobject_put+0x1d/0x50
[<c073620d>] ? rt_mutex_unlock+0xd/0x10
[<c01961f2>] ? rt_up_write+0x22/0x30
[<c05e918d>] ? unlock_policy_rwsem_write+0x2d/0x40
[<c05eab6e>] __cpufreq_remove_dev+0xbe/0x260
[<c019614b>] ? rt_down_write_trylock+0x4b/0x60
[<c07339f3>] cpufreq_cpu_callback+0x70/0x83
[<c073ac5a>] notifier_call_chain+0x7a/0xa0
[<c017a3fe>] __raw_notifier_call_chain+0x1e/0x30
[<c0150494>] __cpu_notify+0x24/0x40
[<c071b7c1>] _cpu_down+0x151/0x350
[<c071b9f0>] cpu_down+0x30/0x50
[<c071d550>] store_online+0x50/0xa7
[<c071d500>] ? acpi_os_map_memory+0xf2/0xf2
[<c052466a>] sysdev_store+0x2a/0x40
[<c02a9ed4>] sysfs_write_file+0xa4/0x100
[<c02450c2>] vfs_write+0xa2/0x170
[<c02a9e30>] ? sysfs_poll+0x90/0x90
[<c02453c8>] sys_write+0x48/0x80
[<c073e15f>] sysenter_do_call+0x12/0x38
Signed-off-by: Yong Zhang <yong.zhang0@...il.com>
---
drivers/cpufreq/cpufreq.c | 20 +++++++-------------
1 files changed, 7 insertions(+), 13 deletions(-)
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 7741f0f..8561182 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -821,16 +821,14 @@ static int cpufreq_add_dev_interface(unsigned int cpu,
goto err_out_kobj_put;
}
- get_online_cpus();
+ raw_spin_lock_irqsave(&cpufreq_driver_lock, flags);
for_each_cpu(j, policy->cpus) {
if (!cpu_online(j))
continue;
- raw_spin_lock_irqsave(&cpufreq_driver_lock, flags);
per_cpu(cpufreq_cpu_data, j) = policy;
per_cpu(cpufreq_policy_cpu, j) = policy->cpu;
- raw_spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
}
- put_online_cpus();
+ raw_spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
ret = cpufreq_add_dev_symlink(cpu, policy);
if (ret)
@@ -972,13 +970,11 @@ static int cpufreq_add_dev(struct sys_device *sys_dev)
err_out_unregister:
- get_online_cpus();
+ raw_spin_lock_irqsave(&cpufreq_driver_lock, flags);
for_each_cpu(j, policy->cpus) {
- raw_spin_lock_irqsave(&cpufreq_driver_lock, flags);
per_cpu(cpufreq_cpu_data, j) = NULL;
- raw_spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
}
- put_online_cpus();
+ raw_spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
kobject_put(&policy->kobj);
wait_for_completion(&policy->kobj_unregister);
@@ -1045,7 +1041,6 @@ static int __cpufreq_remove_dev(struct sys_device *sys_dev)
}
#endif
- raw_spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
#ifdef CONFIG_SMP
#ifdef CONFIG_HOTPLUG_CPU
@@ -1058,17 +1053,14 @@ static int __cpufreq_remove_dev(struct sys_device *sys_dev)
* per_cpu(cpufreq_cpu_data) while holding the lock, and remove
* the sysfs links afterwards.
*/
- get_online_cpus();
if (unlikely(cpumask_weight(data->cpus) > 1)) {
for_each_cpu(j, data->cpus) {
if (j == cpu)
continue;
- raw_spin_lock_irqsave(&cpufreq_driver_lock, flags);
per_cpu(cpufreq_cpu_data, j) = NULL;
- raw_spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
}
}
- put_online_cpus();
+ raw_spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
if (unlikely(cpumask_weight(data->cpus) > 1)) {
for_each_cpu(j, data->cpus) {
@@ -1087,6 +1079,8 @@ static int __cpufreq_remove_dev(struct sys_device *sys_dev)
cpufreq_cpu_put(data);
}
}
+#else
+ raw_spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
#endif
if (cpufreq_driver->target)
--
1.7.1
--
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