Patchwork [v5,22/45] infiniband: ehca: Use get/put_online_cpus_atomic() to prevent CPU offline

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Submitter Srivatsa S. Bhat
Date Jan. 22, 2013, 7:39 a.m.
Message ID <20130122073909.13822.6220.stgit@srivatsabhat.in.ibm.com>
Download mbox | patch
Permalink /patch/214407/
State Not Applicable
Delegated to: David Miller
Headers show

Comments

Srivatsa S. Bhat - Jan. 22, 2013, 7:39 a.m.
Once stop_machine() is gone from the CPU offline path, we won't be able to
depend on preempt_disable() or local_irq_disable() 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: Roland Dreier <roland@kernel.org>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---

 drivers/infiniband/hw/ehca/ehca_irq.c |    8 ++++++++
 1 file changed, 8 insertions(+)


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Patch

diff --git a/drivers/infiniband/hw/ehca/ehca_irq.c b/drivers/infiniband/hw/ehca/ehca_irq.c
index 8615d7c..d61936c 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"
@@ -653,6 +654,9 @@  void ehca_tasklet_eq(unsigned long data)
 	ehca_process_eq((struct ehca_shca*)data, 1);
 }
 
+/*
+ * Must be called under get_online_cpus_atomic() and put_online_cpus_atomic().
+ */
 static int find_next_online_cpu(struct ehca_comp_pool *pool)
 {
 	int cpu;
@@ -703,6 +707,7 @@  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);
 	BUG_ON(!cpu_online(cpu_id));
 
@@ -720,6 +725,7 @@  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 +765,7 @@  static void comp_task_park(unsigned int cpu)
 	list_splice_init(&cct->cq_list, &list);
 	spin_unlock_irq(&cct->task_lock);
 
+	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 +775,7 @@  static void comp_task_park(unsigned int cpu)
 		__queue_comp_task(cq, target, thread);
 	}
 	spin_unlock_irq(&target->task_lock);
+	put_online_cpus_atomic();
 }
 
 static void comp_task_stop(unsigned int cpu, bool online)