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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2015-01-28 14:09:43 -0800
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2015-03-12 15:19:37 -0700
commit528a25b00e1f84eaba6c98e63f58ee0a8e472102 (patch)
tree449e267d06f42020bcaaae7a218710112bedd38e /kernel/cpu.c
parentc199068913c9c5cbb5498e289bb387703e087ea8 (diff)
cpu: Make CPU-offline idle-loop transition point more precise
This commit uses a per-CPU variable to make the CPU-offline code path through the idle loop more precise, so that the outgoing CPU is guaranteed to make it into the idle loop before it is powered off. This commit is in preparation for putting the RCU offline-handling code on this code path, which will eliminate the magic one-jiffy wait that RCU uses as the maximum time for an outgoing CPU to get all the way through the scheduler. The magic one-jiffy wait for incoming CPUs remains a separate issue. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/cpu.c')
-rw-r--r--kernel/cpu.c4
1 files changed, 3 insertions, 1 deletions
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 1972b161c61e..d46b4dae0ca0 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -408,8 +408,10 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
*
* Wait for the stop thread to go away.
*/
- while (!idle_cpu(cpu))
+ while (!per_cpu(cpu_dead_idle, cpu))
cpu_relax();
+ smp_mb(); /* Read from cpu_dead_idle before __cpu_die(). */
+ per_cpu(cpu_dead_idle, cpu) = false;
/* This actually kills the CPU. */
__cpu_die(cpu);

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