From: Sebastian Andrzej Siewior <bige...@linutronix.de>
Some call sites of cpuhp_setup/remove_state[_nocalls]() are within a
cpus_read locked region.
cpuhp_setup/remove_state[_nocalls]() call cpus_read_lock() 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
cpus_read_lock().
Signed-off-by: Sebastian Andrzej Siewior <bige...@linutronix.de>
Signed-off-by: Thomas Gleixner <t...@linutronix.de>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Steven Rostedt <rost...@goodmis.org>
---
include/linux/cpuhotplug.h | 29 +++++++++++++++++++++++++++
kernel/cpu.c | 47 ++++++++++++++++++++++++++++++++++-----------
2 files changed, 65 insertions(+), 11 deletions(-)
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -153,6 +153,11 @@ int __cpuhp_setup_state(enum cpuhp_state
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
@@ -171,6 +176,15 @@ static inline int cpuhp_setup_state(enum
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
@@ -191,6 +205,15 @@ static inline int cpuhp_setup_state_noca
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
@@ -250,6 +273,7 @@ static inline int cpuhp_state_add_instan
}
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
@@ -273,6 +297,11 @@ static inline void cpuhp_remove_state_no
__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
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -1459,7 +1459,7 @@ int __cpuhp_state_add_instance(enum cpuh
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
@@ -1468,25 +1468,27 @@ EXPORT_SYMBOL_GPL(__cpuhp_state_add_inst
* @multi_instance: State is set up for multiple instances which get
* added afterwards.
*
+ * The caller needs to hold cpus read locked 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;
+ lockdep_assert_cpus_held();
+
if (cpuhp_cb_check(state) || !name)
return -EINVAL;
- cpus_read_lock();
mutex_lock(&cpuhp_state_mutex);
ret = cpuhp_store_callbacks(state, name, startup, teardown,
@@ -1522,7 +1524,6 @@ int __cpuhp_setup_state(enum cpuhp_state
}
out:
mutex_unlock(&cpuhp_state_mutex);
- cpus_read_unlock();
/*
* If the requested state is CPUHP_AP_ONLINE_DYN, return the
* dynamically allocated state in case of success.
@@ -1531,6 +1532,22 @@ int __cpuhp_setup_state(enum cpuhp_state
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;
+
+ cpus_read_lock();
+ ret = __cpuhp_setup_state_cpuslocked(state, name, invoke, startup,
+ teardown, multi_instance);
+ cpus_read_unlock();
+ return ret;
+}
EXPORT_SYMBOL(__cpuhp_setup_state);
int __cpuhp_state_remove_instance(enum cpuhp_state state,
@@ -1572,22 +1589,23 @@ int __cpuhp_state_remove_instance(enum c
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 cpus read locked 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));
- cpus_read_lock();
+ lockdep_assert_cpus_held();
mutex_lock(&cpuhp_state_mutex);
if (sp->multi_instance) {
@@ -1615,6 +1633,13 @@ void __cpuhp_remove_state(enum cpuhp_sta
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)
+{
+ cpus_read_lock();
+ __cpuhp_remove_state_cpuslocked(state, invoke);
cpus_read_unlock();
}
EXPORT_SYMBOL(__cpuhp_remove_state);
