Re: [PATCH] hv: Fix unnecessary sleeping in hv_synic_alloc

From: Jia-Ju Bai
Date: Mon Dec 18 2017 - 03:58:41 EST

On 2017/12/18 16:54, Vitaly Kuznetsov wrote:
Jia-Ju Bai <baijiaju1990@xxxxxxxxx> writes:

The kzalloc function is called with GFP_ATOMIC.
But according to driver call graph, it is not in atomic context,
namely no spinlock is held nor in an interrupt handler.

This GFP_ATOMIC is unnecessary, and replace with GFP_KERNEL.

Signed-off-by: Jia-Ju Bai <baijiaju1990@xxxxxxxxx>
drivers/hv/hv.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index 8267439..b0d025a 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -150,7 +150,7 @@ int hv_synic_alloc(void)
int cpu;

hv_context.hv_numa_map = kzalloc(sizeof(struct cpumask) * nr_node_ids,
if (hv_context.hv_numa_map == NULL) {
pr_err("Unable to allocate NUMA map\n");
goto err;
Reviewed-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>

The subject line is not very accurate: GFP_KERNEL you switch too is the
one supporting 'sleep' when there's not enough memory, not
GFP_ATOMIC so you don't actually "Fix unnecessary sleeping". I'd suggest
you use something like "hyper-v: use GFP_KERNEL for hv_context.hv_numa_map"

Thanks for you suggestion :)
Okay, I found my description is not correct, too, sorry.
I will revise it and resubmit the patch.

Jia-Ju Bai