[PATCH v2 21/45] block: Use get/put_online_cpus_atomic() to preventCPU offline

From: Srivatsa S. Bhat
Date: Tue Jun 25 2013 - 16:33:09 EST


Once stop_machine() is gone from the CPU offline path, we won't be able
to depend on disabling preemption to prevent CPUs from going offline
from under us.

Use the get/put_online_cpus_atomic() APIs to prevent CPUs from going
offline, while invoking from atomic context.

Cc: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@xxxxxxxxxxxxxxxxxx>
---

block/blk-softirq.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/block/blk-softirq.c b/block/blk-softirq.c
index 467c8de..bbab3d3 100644
--- a/block/blk-softirq.c
+++ b/block/blk-softirq.c
@@ -58,6 +58,7 @@ static void trigger_softirq(void *data)
*/
static int raise_blk_irq(int cpu, struct request *rq)
{
+ get_online_cpus_atomic();
if (cpu_online(cpu)) {
struct call_single_data *data = &rq->csd;

@@ -66,8 +67,10 @@ static int raise_blk_irq(int cpu, struct request *rq)
data->flags = 0;

__smp_call_function_single(cpu, data, 0);
+ put_online_cpus_atomic();
return 0;
}
+ put_online_cpus_atomic();

return 1;
}

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