4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Thomas Gleixner tglx@linutronix.de
[ Upstream commit 49dfe2a6779717d9c18395684ee31bdc98b22e53 ]
The CPU hotplug callbacks are not covered by lockdep versus the cpu hotplug rwsem.
CPU0 CPU1 cpuhp_setup_state(STATE, startup, teardown); cpus_read_lock(); invoke_callback_on_ap(); kick_hotplug_thread(ap); wait_for_completion(); hotplug_thread_fn() lock(m); do_stuff(); unlock(m);
Lockdep does not know about this dependency and will not trigger on the following code sequence:
lock(m); cpus_read_lock();
Add a lockdep map and connect the initiators lock chain with the hotplug thread lock chain, so potential deadlocks can be detected.
Signed-off-by: Thomas Gleixner tglx@linutronix.de Tested-by: Paul E. McKenney paulmck@linux.vnet.ibm.com Acked-by: Ingo Molnar mingo@kernel.org Cc: Peter Zijlstra peterz@infradead.org Cc: Sebastian Siewior bigeasy@linutronix.de Cc: Steven Rostedt rostedt@goodmis.org Link: http://lkml.kernel.org/r/20170524081549.709375845@linutronix.de Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/cpu.c | 13 +++++++++++++ 1 file changed, 13 insertions(+)
--- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -63,6 +63,12 @@ struct cpuhp_cpu_state {
static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state);
+#if defined(CONFIG_LOCKDEP) && defined(CONFIG_SMP) +static struct lock_class_key cpuhp_state_key; +static struct lockdep_map cpuhp_state_lock_map = + STATIC_LOCKDEP_MAP_INIT("cpuhp_state", &cpuhp_state_key); +#endif + /** * cpuhp_step - Hotplug state machine step * @name: Name of the step @@ -563,6 +569,7 @@ static void cpuhp_thread_fun(unsigned in
st->should_run = false;
+ lock_map_acquire(&cpuhp_state_lock_map); /* Single callback invocation for [un]install ? */ if (st->single) { if (st->cb_state < CPUHP_AP_ONLINE) { @@ -594,6 +601,7 @@ static void cpuhp_thread_fun(unsigned in else if (st->state > st->target) ret = cpuhp_ap_offline(cpu, st); } + lock_map_release(&cpuhp_state_lock_map); st->result = ret; complete(&st->done); } @@ -608,6 +616,9 @@ cpuhp_invoke_ap_callback(int cpu, enum c if (!cpu_online(cpu)) return 0;
+ lock_map_acquire(&cpuhp_state_lock_map); + lock_map_release(&cpuhp_state_lock_map); + /* * If we are up and running, use the hotplug thread. For early calls * we invoke the thread function directly. @@ -651,6 +662,8 @@ static int cpuhp_kick_ap_work(unsigned i enum cpuhp_state state = st->state;
trace_cpuhp_enter(cpu, st->target, state, cpuhp_kick_ap_work); + lock_map_acquire(&cpuhp_state_lock_map); + lock_map_release(&cpuhp_state_lock_map); __cpuhp_kick_ap_work(st); wait_for_completion(&st->done); trace_cpuhp_exit(cpu, st->state, state, st->result);