Commit-ID: 4205e4786d0b9fc3b4fec7b1910cf645a0468307
Gitweb: http://git.kernel.org/tip/4205e4786d0b9fc3b4fec7b1910cf645a0468307
Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate: Tue, 10 Jan 2017 14:01:05 +0100
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Mon, 16 Jan 2017 13:20:05 +0100
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@xxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Sebastian Sewior <bigeasy@xxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1701101353010.3401@nanos
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
include/linux/cpuhotplug.h | 2 ++
kernel/cpu.c | 22 ++++++++++++++++++----
2 files changed, 20 insertions(+), 4 deletions(-)
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 20bfefb..d936a00 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -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,
diff --git a/kernel/cpu.c b/kernel/cpu.c
index f75c4d0..c475063 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -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;
--
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