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Commit 4205e478 authored by Thomas Gleixner's avatar Thomas Gleixner
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cpu/hotplug: Provide dynamic range for prepare stage 



Mathieu reported that the LTTNG modules are broken as of 4.10-rc1 due to
the removal of the cpu hotplug notifiers.

Usually I don't care much about out of tree modules, but LTTNG is widely
used in distros. There are two ways to solve that:

1) Reserve a hotplug state for LTTNG

2) Add a dynamic range for the prepare states.

While #1 is the simplest solution, #2 is the proper one as we can convert
in tree users, which do not care about ordering, to the dynamic range as
well.

Add a dynamic range which allows LTTNG to request states in the prepare
stage.

Reported-and-tested-by: default avatarMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Sewior <bigeasy@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1701101353010.3401@nanos


Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 7e164ce4

include/linux/cpuhotplug.h

+2 −0
Original line number Diff line number Diff line
@@ -74,6 +74,8 @@ enum cpuhp_state { 
	CPUHP_ZCOMP_PREPARE,

	CPUHP_TIMERS_DEAD,

	CPUHP_MIPS_SOC_PREPARE,

	CPUHP_BP_PREPARE_DYN,

	CPUHP_BP_PREPARE_DYN_END		= CPUHP_BP_PREPARE_DYN + 20,

	CPUHP_BRINGUP_CPU,

	CPUHP_AP_IDLE_DEAD,

	CPUHP_AP_OFFLINE,

kernel/cpu.c

+18 −4
Original line number Diff line number Diff line
@@ -1302,10 +1302,24 @@ static int cpuhp_cb_check(enum cpuhp_state state) 
 */

static int cpuhp_reserve_state(enum cpuhp_state state)

{

	enum cpuhp_state i;

	enum cpuhp_state i, end;

	struct cpuhp_step *step;



	for (i = CPUHP_AP_ONLINE_DYN; i <= CPUHP_AP_ONLINE_DYN_END; i++) {

		if (!cpuhp_ap_states[i].name)

	switch (state) {

	case CPUHP_AP_ONLINE_DYN:

		step = cpuhp_ap_states + CPUHP_AP_ONLINE_DYN;

		end = CPUHP_AP_ONLINE_DYN_END;

		break;

	case CPUHP_BP_PREPARE_DYN:

		step = cpuhp_bp_states + CPUHP_BP_PREPARE_DYN;

		end = CPUHP_BP_PREPARE_DYN_END;

		break;

	default:

		return -EINVAL;

	}



	for (i = state; i <= end; i++, step++) {

		if (!step->name)

			return i;

	}

	WARN(1, "No more dynamic states available for CPU hotplug\n");
@@ -1323,7 +1337,7 @@ static int cpuhp_store_callbacks(enum cpuhp_state state, const char *name, 


	mutex_lock(&cpuhp_state_mutex);



	if (state == CPUHP_AP_ONLINE_DYN) {

	if (state == CPUHP_AP_ONLINE_DYN || state == CPUHP_BP_PREPARE_DYN) {

		ret = cpuhp_reserve_state(state);

		if (ret < 0)

			goto out;