Subject: + cpu-hotplug-stop-machine-plug-race-window-that-leads-to-ipi-to-offline-cpu-v3.patch added to -mm tree
To: srivatsa.bhat@xxxxxxxxxxxxxxxxxx,bp@xxxxxxx,ego@xxxxxxxxxxxxxxxxxx,fweisbec@xxxxxxxxx,hch@xxxxxxxxxxxxx,mgalbraith@xxxxxxx,mgorman@xxxxxxx,mingo@xxxxxxxxxx,oleg@xxxxxxxxxx,paulmck@xxxxxxxxxxxxxxxxxx,peterz@xxxxxxxxxxxxx,riel@xxxxxxxxxx,rjw@xxxxxxxxxxxxx,rostedt@xxxxxxxxxxx,rusty@xxxxxxxxxxxxxxx,tglx@xxxxxxxxxxxxx,tj@xxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Mon, 12 May 2014 14:58:18 -0700
The patch titled
Subject: cpu-hotplug-stop-machine-plug-race-window-that-leads-to-ipi-to-offline-cpu-v3
has been added to the -mm tree. Its filename is
cpu-hotplug-stop-machine-plug-race-window-that-leads-to-ipi-to-offline-cpu-v3.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/cpu-hotplug-stop-machine-plug-race-window-that-leads-to-ipi-to-offline-cpu-v3.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/cpu-hotplug-stop-machine-plug-race-window-that-leads-to-ipi-to-offline-cpu-v3.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: "Srivatsa S. Bhat" <srivatsa.bhat@xxxxxxxxxxxxxxxxxx>
Subject: cpu-hotplug-stop-machine-plug-race-window-that-leads-to-ipi-to-offline-cpu-v3
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@xxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Mike Galbraith <mgalbraith@xxxxxxx>
Cc: Gautham R Shenoy <ego@xxxxxxxxxxxxxxxxxx>
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Rafael J. Wysocki <rjw@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/stop_machine.c | 43 +++++++++++++++++-----------------------
1 file changed, 19 insertions(+), 24 deletions(-)
diff -puN kernel/stop_machine.c~cpu-hotplug-stop-machine-plug-race-window-that-leads-to-ipi-to-offline-cpu-v3 kernel/stop_machine.c
--- a/kernel/stop_machine.c~cpu-hotplug-stop-machine-plug-race-window-that-leads-to-ipi-to-offline-cpu-v3
+++ a/kernel/stop_machine.c
@@ -130,8 +130,10 @@ enum multi_stop_state {
MULTI_STOP_NONE,
/* Awaiting everyone to be scheduled. */
MULTI_STOP_PREPARE,
- /* Disable interrupts. */
- MULTI_STOP_DISABLE_IRQ,
+ /* Disable interrupts on CPUs not in ->active_cpus mask. */
+ MULTI_STOP_DISABLE_IRQ_INACTIVE,
+ /* Disable interrupts on CPUs in ->active_cpus mask. */
+ MULTI_STOP_DISABLE_IRQ_ACTIVE,
/* Run the function */
MULTI_STOP_RUN,
/* Exit */
@@ -165,13 +167,12 @@ static void ack_state(struct multi_stop_
set_state(msdata, msdata->state + 1);
}
-
/* This is the cpu_stop function which stops the CPU. */
static int multi_cpu_stop(void *data)
{
struct multi_stop_data *msdata = data;
enum multi_stop_state curstate = MULTI_STOP_NONE;
- int cpu = smp_processor_id(), num_active_cpus, err = 0;
+ int cpu = smp_processor_id(), err = 0;
unsigned long flags;
bool is_active;
@@ -181,13 +182,10 @@ static int multi_cpu_stop(void *data)
*/
local_save_flags(flags);
- if (!msdata->active_cpus) {
+ if (!msdata->active_cpus)
is_active = cpu == cpumask_first(cpu_online_mask);
- num_active_cpus = 1;
- } else {
+ else
is_active = cpumask_test_cpu(cpu, msdata->active_cpus);
- num_active_cpus = cpumask_weight(msdata->active_cpus);
- }
/* Simple state machine */
do {
@@ -197,26 +195,23 @@ static int multi_cpu_stop(void *data)
/*
* In the case of CPU offline, we don't want the other CPUs to
* send IPIs to the active_cpu (the one going offline) after it
- * has entered the _DISABLE_IRQ state (because, then it will
- * notice the IPIs only after it goes offline). So ensure that
- * the active_cpu always follows the others while entering
- * each subsequent state in this state-machine.
- *
- * msdata->thread_ack tracks the number of CPUs that are yet to
- * move to the next state, during each transition. So make the
- * active_cpu(s) wait until ->thread_ack indicates that the
- * active_cpus are the only ones left to complete the transition.
+ * has disabled interrupts in the _DISABLE_IRQ state (because,
+ * then it will notice the IPIs only after it goes offline). So
+ * we split this state into _INACTIVE and _ACTIVE, and thereby
+ * ensure that the active_cpu disables interrupts only after
+ * the other CPUs do the same thing.
*/
- if (is_active) {
- /* Wait until all the non-active threads ack the state */
- while (atomic_read(&msdata->thread_ack) > num_active_cpus)
- cpu_relax();
- }
if (msdata->state != curstate) {
curstate = msdata->state;
switch (curstate) {
- case MULTI_STOP_DISABLE_IRQ:
+ case MULTI_STOP_DISABLE_IRQ_INACTIVE:
+ if (is_active)
+ break;
+
+ /* Else, fall-through */
+
+ case MULTI_STOP_DISABLE_IRQ_ACTIVE:
local_irq_disable();
hard_irq_disable();
break;
_
Patches currently in -mm which might be from srivatsa.bhat@xxxxxxxxxxxxxxxxxx are
smp-print-more-useful-debug-info-upon-receiving-ipi-on-an-offline-cpu.patch
smp-print-more-useful-debug-info-upon-receiving-ipi-on-an-offline-cpu-fix.patch
cpu-hotplug-stop-machine-plug-race-window-that-leads-to-ipi-to-offline-cpu.patch
cpu-hotplug-stop-machine-plug-race-window-that-leads-to-ipi-to-offline-cpu-v3.patch
linux-next.patch
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
