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Subject[tip:smp/hotplug] cpu/hotplug: Provide cpuhp_setup/remove_state[_nocalls]_cpuslocked()
Commit-ID:  6fd1f038ff919b765d1edc877ce14b9f20a703f7
Gitweb: http://git.kernel.org/tip/6fd1f038ff919b765d1edc877ce14b9f20a703f7
Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
AuthorDate: Tue, 18 Apr 2017 19:04:43 +0200
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Thu, 20 Apr 2017 13:08:50 +0200

cpu/hotplug: Provide cpuhp_setup/remove_state[_nocalls]_cpuslocked()

Some call sites of cpuhp_setup/remove_state[_nocalls]() are within a
get_online_cpus() protected region.

cpuhp_setup/remove_state[_nocalls]() call get_online_cpus() as well, which
is possible in the current implementation but prevents converting the
hotplug locking to a percpu rwsem.

Provide locked versions of the interfaces to avoid nested calls to
get_online_cpus().

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20170418170552.448563593@linutronix.de

---
include/linux/cpuhotplug.h | 29 +++++++++++++++++++++++++++++
kernel/cpu.c | 45 +++++++++++++++++++++++++++++++++------------
2 files changed, 62 insertions(+), 12 deletions(-)

diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 62d240e..5b33837 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -151,6 +151,11 @@ int __cpuhp_setup_state(enum cpuhp_state state, const char *name, bool invoke,
int (*startup)(unsigned int cpu),
int (*teardown)(unsigned int cpu), bool multi_instance);

+int __cpuhp_setup_state_cpuslocked(enum cpuhp_state state, const char *name,
+ bool invoke,
+ int (*startup)(unsigned int cpu),
+ int (*teardown)(unsigned int cpu),
+ bool multi_instance);
/**
* cpuhp_setup_state - Setup hotplug state callbacks with calling the callbacks
* @state: The state for which the calls are installed
@@ -169,6 +174,15 @@ static inline int cpuhp_setup_state(enum cpuhp_state state,
return __cpuhp_setup_state(state, name, true, startup, teardown, false);
}

+static inline int cpuhp_setup_state_cpuslocked(enum cpuhp_state state,
+ const char *name,
+ int (*startup)(unsigned int cpu),
+ int (*teardown)(unsigned int cpu))
+{
+ return __cpuhp_setup_state_cpuslocked(state, name, true, startup,
+ teardown, false);
+}
+
/**
* cpuhp_setup_state_nocalls - Setup hotplug state callbacks without calling the
* callbacks
@@ -189,6 +203,15 @@ static inline int cpuhp_setup_state_nocalls(enum cpuhp_state state,
false);
}

+static inline int cpuhp_setup_state_nocalls_cpuslocked(enum cpuhp_state state,
+ const char *name,
+ int (*startup)(unsigned int cpu),
+ int (*teardown)(unsigned int cpu))
+{
+ return __cpuhp_setup_state_cpuslocked(state, name, false, startup,
+ teardown, false);
+}
+
/**
* cpuhp_setup_state_multi - Add callbacks for multi state
* @state: The state for which the calls are installed
@@ -248,6 +271,7 @@ static inline int cpuhp_state_add_instance_nocalls(enum cpuhp_state state,
}

void __cpuhp_remove_state(enum cpuhp_state state, bool invoke);
+void __cpuhp_remove_state_cpuslocked(enum cpuhp_state state, bool invoke);

/**
* cpuhp_remove_state - Remove hotplug state callbacks and invoke the teardown
@@ -271,6 +295,11 @@ static inline void cpuhp_remove_state_nocalls(enum cpuhp_state state)
__cpuhp_remove_state(state, false);
}

+static inline void cpuhp_remove_state_nocalls_cpuslocked(enum cpuhp_state state)
+{
+ __cpuhp_remove_state_cpuslocked(state, false);
+}
+
/**
* cpuhp_remove_multi_state - Remove hotplug multi state callback
* @state: The state for which the calls are removed
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 37b223e..92e5a91 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -1457,7 +1457,7 @@ unlock:
EXPORT_SYMBOL_GPL(__cpuhp_state_add_instance);

/**
- * __cpuhp_setup_state - Setup the callbacks for an hotplug machine state
+ * __cpuhp_setup_state_cpuslocked - Setup the callbacks for an hotplug machine state
* @state: The state to setup
* @invoke: If true, the startup function is invoked for cpus where
* cpu state >= @state
@@ -1466,17 +1466,18 @@ EXPORT_SYMBOL_GPL(__cpuhp_state_add_instance);
* @multi_instance: State is set up for multiple instances which get
* added afterwards.
*
+ * The caller needs to hold get_online_cpus() while calling this function.
* Returns:
* On success:
* Positive state number if @state is CPUHP_AP_ONLINE_DYN
* 0 for all other states
* On failure: proper (negative) error code
*/
-int __cpuhp_setup_state(enum cpuhp_state state,
- const char *name, bool invoke,
- int (*startup)(unsigned int cpu),
- int (*teardown)(unsigned int cpu),
- bool multi_instance)
+int __cpuhp_setup_state_cpuslocked(enum cpuhp_state state,
+ const char *name, bool invoke,
+ int (*startup)(unsigned int cpu),
+ int (*teardown)(unsigned int cpu),
+ bool multi_instance)
{
int cpu, ret = 0;
bool dynstate;
@@ -1484,7 +1485,6 @@ int __cpuhp_setup_state(enum cpuhp_state state,
if (cpuhp_cb_check(state) || !name)
return -EINVAL;

- get_online_cpus();
mutex_lock(&cpuhp_state_mutex);

ret = cpuhp_store_callbacks(state, name, startup, teardown,
@@ -1520,7 +1520,6 @@ 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
* dynamically allocated state in case of success.
@@ -1529,6 +1528,22 @@ out:
return state;
return ret;
}
+EXPORT_SYMBOL(__cpuhp_setup_state_cpuslocked);
+
+int __cpuhp_setup_state(enum cpuhp_state state,
+ const char *name, bool invoke,
+ int (*startup)(unsigned int cpu),
+ int (*teardown)(unsigned int cpu),
+ bool multi_instance)
+{
+ int ret;
+
+ get_online_cpus();
+ ret = __cpuhp_setup_state_cpuslocked(state, name, invoke, startup,
+ teardown, multi_instance);
+ put_online_cpus();
+ return ret;
+}
EXPORT_SYMBOL(__cpuhp_setup_state);

int __cpuhp_state_remove_instance(enum cpuhp_state state,
@@ -1570,23 +1585,22 @@ remove:
EXPORT_SYMBOL_GPL(__cpuhp_state_remove_instance);

/**
- * __cpuhp_remove_state - Remove the callbacks for an hotplug machine state
+ * __cpuhp_remove_state_cpuslocked - Remove the callbacks for an hotplug machine state
* @state: The state to remove
* @invoke: If true, the teardown function is invoked for cpus where
* cpu state >= @state
*
+ * The caller needs to hold get_online_cpus() while calling this function.
* The teardown callback is currently not allowed to fail. Think
* about module removal!
*/
-void __cpuhp_remove_state(enum cpuhp_state state, bool invoke)
+void __cpuhp_remove_state_cpuslocked(enum cpuhp_state state, bool invoke)
{
struct cpuhp_step *sp = cpuhp_get_step(state);
int cpu;

BUG_ON(cpuhp_cb_check(state));

- get_online_cpus();
-
mutex_lock(&cpuhp_state_mutex);
if (sp->multi_instance) {
WARN(!hlist_empty(&sp->list),
@@ -1613,6 +1627,13 @@ void __cpuhp_remove_state(enum cpuhp_state state, bool invoke)
remove:
cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
mutex_unlock(&cpuhp_state_mutex);
+}
+EXPORT_SYMBOL(__cpuhp_remove_state_cpuslocked);
+
+void __cpuhp_remove_state(enum cpuhp_state state, bool invoke)
+{
+ get_online_cpus();
+ __cpuhp_remove_state_cpuslocked(state, invoke);
put_online_cpus();
}
EXPORT_SYMBOL(__cpuhp_remove_state);
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