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Subject[GIT pull] smp/hotplug fix for 4.11
Linus,

please pull the latest smp-urgent-for-linus git tree from:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git smp-urgent-for-linus

A single fix preventing the concurrent execution of the CPU hotplug
callback install/invocation machinery. Long standing bug caused by a
massive brain slip of that Gleixner dude, which went unnoticed for almost a
year.

Thanks,

tglx

------------------>
Sebastian Andrzej Siewior (1):
cpu/hotplug: Serialize callback invocations proper


kernel/cpu.c | 28 ++++++++++++++--------------
1 file 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 @@ int __cpuhp_state_remove_instance(enum cpuhp_state state,
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);
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