[PATCH 23/45] infiniband: ehca: Use get/put_online_cpus_atomic() toprevent CPU offline

From: Srivatsa S. Bhat
Date: Sun Jun 23 2013 - 09:46:49 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: Hoang-Nam Nguyen <hnguyen@xxxxxxxxxx>
Cc: Christoph Raisch <raisch@xxxxxxxxxx>
Cc: Roland Dreier <roland@xxxxxxxxxx>
Cc: Sean Hefty <sean.hefty@xxxxxxxxx>
Cc: Hal Rosenstock <hal.rosenstock@xxxxxxxxx>
Cc: linux-rdma@xxxxxxxxxxxxxxx
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@xxxxxxxxxxxxxxxxxx>

drivers/infiniband/hw/ehca/ehca_irq.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/drivers/infiniband/hw/ehca/ehca_irq.c b/drivers/infiniband/hw/ehca/ehca_irq.c
index 8615d7c..ace901e 100644
--- a/drivers/infiniband/hw/ehca/ehca_irq.c
+++ b/drivers/infiniband/hw/ehca/ehca_irq.c
@@ -43,6 +43,7 @@

#include <linux/slab.h>
#include <linux/smpboot.h>
+#include <linux/cpu.h>

#include "ehca_classes.h"
#include "ehca_irq.h"
@@ -703,6 +704,7 @@ static void queue_comp_task(struct ehca_cq *__cq)
int cq_jobs;
unsigned long flags;

+ get_online_cpus_atomic();
cpu_id = find_next_online_cpu(pool);

@@ -720,6 +722,7 @@ static void queue_comp_task(struct ehca_cq *__cq)
BUG_ON(!cct || !thread);
__queue_comp_task(__cq, cct, thread);
+ put_online_cpus_atomic();

static void run_comp_task(struct ehca_cpu_comp_task *cct)
@@ -759,6 +762,7 @@ static void comp_task_park(unsigned int cpu)
list_splice_init(&cct->cq_list, &list);

+ get_online_cpus_atomic();
cpu = find_next_online_cpu(pool);
target = per_cpu_ptr(pool->cpu_comp_tasks, cpu);
thread = *per_cpu_ptr(pool->cpu_comp_threads, cpu);
@@ -768,6 +772,7 @@ static void comp_task_park(unsigned int cpu)
__queue_comp_task(cq, target, thread);
+ put_online_cpus_atomic();

static void comp_task_stop(unsigned int cpu, bool online)

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