[RFC v0 1/9] smpboot: Add a separate CPU state when a surviving CPU times out

From: Daniel Wagner
Date: Fri Sep 04 2015 - 09:38:44 EST

The CPU_DEAD_FROZEN state is abused to report to cpu_wait_death() that
the operation timeout. It has nothing to do with the pm freezing
process. Introduce a new state to allow proper distinction between the
states and also prepares the code to get rid of all FROZEN states.

This was intruced in

8038dad7e888581266c76df15d70ca457a3c5910 smpboot: Add common code for notification from dying CPU
2a442c9c6453d3d043dfd89f2e03a1deff8a6f06 x86: Use common outgoing-CPU-notification code

Signed-off-by: Daniel Wagner <daniel.wagner@xxxxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Cc: Chris Metcalf <cmetcalf@xxxxxxxxxx>
Cc: David Vrabel <david.vrabel@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: x86@xxxxxxxxxx
Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
arch/x86/xen/smp.c | 2 +-
include/linux/cpu.h | 2 ++
kernel/smpboot.c | 4 ++--
3 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index 8648438..7a8bc03 100644
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -740,7 +740,7 @@ static int xen_hvm_cpu_up(unsigned int cpu, struct task_struct *tidle)
* This can happen if CPU was offlined earlier and
* offlining timed out in common_cpu_die().
- if (cpu_report_state(cpu) == CPU_DEAD_FROZEN) {
+ if (cpu_report_state(cpu) == CPU_DEAD_TIMEOUT) {
diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index 23c30bd..381ea8a 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -101,6 +101,8 @@ enum {
* idle loop. */
#define CPU_BROKEN 0x000C /* CPU (unsigned)v did not die properly,
* perhaps due to preemption. */
+#define CPU_DEAD_TIMEOUT 0x000D /* CPU (unsigned)v surviving CPU timed
+ out */

/* Used for CPU hotplug events occurring while tasks are frozen due to a suspend
* operation in progress
diff --git a/kernel/smpboot.c b/kernel/smpboot.c
index 7c434c3..e37efbf 100644
--- a/kernel/smpboot.c
+++ b/kernel/smpboot.c
@@ -505,7 +505,7 @@ update_state:
* Called by the outgoing CPU to report its successful death. Return
* false if this report follows the surviving CPU's timing out.
- * A separate "CPU_DEAD_FROZEN" is used when the surviving CPU
+ * A separate "CPU_DEAD_TIMEOUT" is used when the surviving CPU
* timed out. This approach allows architectures to omit calls to
* cpu_check_up_prepare() and cpu_set_state_online() without defeating
* the next cpu_wait_death()'s polling loop.
@@ -521,7 +521,7 @@ bool cpu_report_death(void)
if (oldstate != CPU_BROKEN)
newstate = CPU_DEAD;
- newstate = CPU_DEAD_FROZEN;
+ newstate = CPU_DEAD_TIMEOUT;
} while (atomic_cmpxchg(&per_cpu(cpu_hotplug_state, cpu),
oldstate, newstate) != oldstate);
return newstate == CPU_DEAD;

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