[13/13] crypto: n2 - Replace racy task affinity logic

Commit Message

Thomas Gleixner April 12, 2017, 8:07 p.m. UTC

spu_queue_register() needs to invoke setup functions on a particular
CPU. This is achieved by temporarily setting the affinity of the
calling user space thread to the requested CPU and reset it to the original
affinity afterwards.

That's racy vs. CPU hotplug and concurrent affinity settings for that
thread resulting in code executing on the wrong CPU and overwriting the
new affinity setting.

Replace it by using work_on_cpu_safe() which guarantees to run the code on
the requested CPU or to fail in case the CPU is offline.

Signed-off-by: Thomas Gleixner <[e-mail]>
Cc: Herbert Xu <[e-mail]>
Cc: "David S. Miller" <[e-mail]>
Cc: [e-mail]
---
 drivers/crypto/n2_core.c |   31 ++++++++++++++++---------------
 1 file changed, 16 insertions(+), 15 deletions(-)

Comments

Herbert Xu April 13, 2017, 4:56 a.m. UTC | #1

On Wed, Apr 12, 2017 at 10:07:39PM +0200, Thomas Gleixner wrote:
> spu_queue_register() needs to invoke setup functions on a particular
> CPU. This is achieved by temporarily setting the affinity of the
> calling user space thread to the requested CPU and reset it to the original
> affinity afterwards.
> 
> That's racy vs. CPU hotplug and concurrent affinity settings for that
> thread resulting in code executing on the wrong CPU and overwriting the
> new affinity setting.
> 
> Replace it by using work_on_cpu_safe() which guarantees to run the code on
> the requested CPU or to fail in case the CPU is offline.
> 
> Signed-off-by: Thomas Gleixner <[e-mail]>
> Cc: Herbert Xu <[e-mail]>
> Cc: "David S. Miller" <[e-mail]>
> Cc: [e-mail]

Acked-by: Herbert Xu <[e-mail]>

Patch

--- a/drivers/crypto/n2_core.c
+++ b/drivers/crypto/n2_core.c
@@ -65,6 +65,11 @@  struct spu_queue {
 	struct list_head	list;
 };
 
+struct spu_qreg {
+	struct spu_queue	*queue;
+	unsigned long		type;
+};
+
 static struct spu_queue **cpu_to_cwq;
 static struct spu_queue **cpu_to_mau;
 
@@ -1631,31 +1636,27 @@  static void queue_cache_destroy(void)
 	kmem_cache_destroy(queue_cache[HV_NCS_QTYPE_CWQ - 1]);
 }
 
-static int spu_queue_register(struct spu_queue *p, unsigned long q_type)
+static long spu_queue_register_workfn(void *arg)
 {
-	cpumask_var_t old_allowed;
+	struct spu_qreg *qr = arg;
+	struct spu_queue *p = qr->queue;
+	unsigned long q_type = qr->type;
 	unsigned long hv_ret;
 
-	if (cpumask_empty(&p->sharing))
-		return -EINVAL;
-
-	if (!alloc_cpumask_var(&old_allowed, GFP_KERNEL))
-		return -ENOMEM;
-
-	cpumask_copy(old_allowed, &current->cpus_allowed);
-
-	set_cpus_allowed_ptr(current, &p->sharing);
-
 	hv_ret = sun4v_ncs_qconf(q_type, __pa(p->q),
 				 CWQ_NUM_ENTRIES, &p->qhandle);
 	if (!hv_ret)
 		sun4v_ncs_sethead_marker(p->qhandle, 0);
 
-	set_cpus_allowed_ptr(current, old_allowed);
+	return hv_ret ? -EINVAL : 0;
+}
 
-	free_cpumask_var(old_allowed);
+static int spu_queue_register(struct spu_queue *p, unsigned long q_type)
+{
+	int cpu = cpumask_any_and(&p->sharing, cpu_online_mask);
+	struct spu_qreg qr = { .queue = p, .type = q_type };
 
-	return (hv_ret ? -EINVAL : 0);
+	return work_on_cpu_safe(cpu, &qr);
 }
 
 static int spu_queue_setup(struct spu_queue *p)