cpu/hotplug: Provide dynamic range for prepare stage (4205e478) · Commits · 戴 / test

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:

Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Signed-off-by:

Thomas Gleixner <tglx@linutronix.de> Reviewed-by:

Mathieu 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:

Thomas Gleixner <tglx@linutronix.de>

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;

Admin message