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

[Daniel Wagner <daniel.wagner@xxxxxxxxxxxx>]

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) {
                xen_smp_intr_free(cpu);
                xen_uninit_lock_cpu(cpu);
        }
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;
                else
-                       newstate = CPU_DEAD_FROZEN;
+                       newstate = CPU_DEAD_TIMEOUT;
        } while (atomic_cmpxchg(&per_cpu(cpu_hotplug_state, cpu),
                                oldstate, newstate) != oldstate);
        return newstate == CPU_DEAD;
-- 
2.4.3


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