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SubjectRe: [PATCH v2 6/8] IB/hns: Replace counting semaphore event_sem with wait_event
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On Tuesday, October 25, 2016 5:31:57 PM CEST Binoy Jayan wrote:
> static int __hns_roce_cmd_mbox_wait(struct hns_roce_dev *hr_dev, u64 in_param,
> u64 out_param, unsigned long in_modifier,
> @@ -198,11 +218,12 @@ static int __hns_roce_cmd_mbox_wait(struct hns_roce_dev *hr_dev, u64 in_param,
> struct hns_roce_cmdq *cmd = &hr_dev->cmd;
> struct device *dev = &hr_dev->pdev->dev;
> struct hns_roce_cmd_context *context;
> - int ret = 0;
> + int orig_free_head, ret = 0;
> +
> + wait_event(cmd->wq, (orig_free_head = atomic_free_node(cmd, -1)) != -1);
>
> spin_lock(&cmd->context_lock);
> - WARN_ON(cmd->free_head < 0);
> - context = &cmd->context[cmd->free_head];
> + context = &cmd->context[orig_free_head];
> context->token += cmd->token_mask + 1;
> cmd->free_head = context->next;
> spin_unlock(&cmd->context_lock);
>

You get the lock in atomic_free_node() and then again right after that.
Why not combine the two and only take the lock inside of that
function that returns a context?

Arnd

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