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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: 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>
This commit is contained in:
Thomas Gleixner 2017-01-10 14:01:05 +01:00
parent 7e164ce4e8
commit 4205e4786d
2 changed files with 20 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/cpuhotplug.h
View File

@ -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,

22
kernel/cpu.c
View File

@ -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;