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authorSebastian Andrzej Siewior <bigeasy@linutronix.de>2017-03-14 16:06:45 +0100
committerThomas Gleixner <tglx@linutronix.de>2017-03-14 19:19:27 +0100
commitdc434e056fe1dada20df7ba07f32739d3a701adf (patch)
treef7756d35699b3a27b358a3d29e08220a18ef06c5
parent4495c08e84729385774601b5146d51d9e5849f81 (diff)
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cpu/hotplug: Serialize callback invocations proper
The setup/remove_state/instance() functions in the hotplug core code are serialized against concurrent CPU hotplug, but unfortunately not serialized against themself. As a consequence a concurrent invocation of these function results in corruption of the callback machinery because two instances try to invoke callbacks on remote cpus at the same time. This results in missing callback invocations and initiator threads waiting forever on the completion. The obvious solution to replace get_cpu_online() with cpu_hotplug_begin() is not possible because at least one callsite calls into these functions from a get_online_cpu() locked region. Extend the protection scope of the cpuhp_state_mutex from solely protecting the state arrays to cover the callback invocation machinery as well. Fixes: 5b7aa87e0482 ("cpu/hotplug: Implement setup/removal interface") Reported-and-tested-by: Bart Van Assche <Bart.VanAssche@sandisk.com> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: hpa@zytor.com Cc: mingo@kernel.org Cc: akpm@linux-foundation.org Cc: torvalds@linux-foundation.org Link: http://lkml.kernel.org/r/20170314150645.g4tdyoszlcbajmna@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
-rw-r--r--kernel/cpu.c28
1 files changed, 14 insertions, 14 deletions
diff --git a/kernel/cpu.c b/kernel/cpu.c
index f7c063239fa5..37b223e4fc05 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -1335,26 +1335,21 @@ static int cpuhp_store_callbacks(enum cpuhp_state state, const char *name,
struct cpuhp_step *sp;
int ret = 0;
- mutex_lock(&cpuhp_state_mutex);
-
if (state == CPUHP_AP_ONLINE_DYN || state == CPUHP_BP_PREPARE_DYN) {
ret = cpuhp_reserve_state(state);
if (ret < 0)
- goto out;
+ return ret;
state = ret;
}
sp = cpuhp_get_step(state);
- if (name && sp->name) {
- ret = -EBUSY;
- goto out;
- }
+ if (name && sp->name)
+ return -EBUSY;
+
sp->startup.single = startup;
sp->teardown.single = teardown;
sp->name = name;
sp->multi_instance = multi_instance;
INIT_HLIST_HEAD(&sp->list);
-out:
- mutex_unlock(&cpuhp_state_mutex);
return ret;
}
@@ -1428,6 +1423,7 @@ int __cpuhp_state_add_instance(enum cpuhp_state state, struct hlist_node *node,
return -EINVAL;
get_online_cpus();
+ mutex_lock(&cpuhp_state_mutex);
if (!invoke || !sp->startup.multi)
goto add_node;
@@ -1447,16 +1443,14 @@ int __cpuhp_state_add_instance(enum cpuhp_state state, struct hlist_node *node,
if (ret) {
if (sp->teardown.multi)
cpuhp_rollback_install(cpu, state, node);
- goto err;
+ goto unlock;
}
}
add_node:
ret = 0;
- mutex_lock(&cpuhp_state_mutex);
hlist_add_head(node, &sp->list);
+unlock:
mutex_unlock(&cpuhp_state_mutex);
-
-err:
put_online_cpus();
return ret;
}
@@ -1491,6 +1485,7 @@ int __cpuhp_setup_state(enum cpuhp_state state,
return -EINVAL;
get_online_cpus();
+ mutex_lock(&cpuhp_state_mutex);
ret = cpuhp_store_callbacks(state, name, startup, teardown,
multi_instance);
@@ -1524,6 +1519,7 @@ int __cpuhp_setup_state(enum cpuhp_state state,
}
}
out:
+ mutex_unlock(&cpuhp_state_mutex);
put_online_cpus();
/*
* If the requested state is CPUHP_AP_ONLINE_DYN, return the
@@ -1547,6 +1543,8 @@ int __cpuhp_state_remove_instance(enum cpuhp_state state,
return -EINVAL;
get_online_cpus();
+ mutex_lock(&cpuhp_state_mutex);
+
if (!invoke || !cpuhp_get_teardown_cb(state))
goto remove;
/*
@@ -1563,7 +1561,6 @@ int __cpuhp_state_remove_instance(enum cpuhp_state state,
}
remove:
- mutex_lock(&cpuhp_state_mutex);
hlist_del(node);
mutex_unlock(&cpuhp_state_mutex);
put_online_cpus();
@@ -1571,6 +1568,7 @@ remove:
return 0;
}
EXPORT_SYMBOL_GPL(__cpuhp_state_remove_instance);
+
/**
* __cpuhp_remove_state - Remove the callbacks for an hotplug machine state
* @state: The state to remove
@@ -1589,6 +1587,7 @@ void __cpuhp_remove_state(enum cpuhp_state state, bool invoke)
get_online_cpus();
+ mutex_lock(&cpuhp_state_mutex);
if (sp->multi_instance) {
WARN(!hlist_empty(&sp->list),
"Error: Removing state %d which has instances left.\n",
@@ -1613,6 +1612,7 @@ void __cpuhp_remove_state(enum cpuhp_state state, bool invoke)
}
remove:
cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
+ mutex_unlock(&cpuhp_state_mutex);
put_online_cpus();
}
EXPORT_SYMBOL(__cpuhp_remove_state);