[Devel] Re: [PATCH] c/r: coordinator to report correct error on restart failure

[Serge E. Hallyn]

Quoting Oren Laadan (orenl at librato.com):
> If restart fails it is usually due to an error for a restoring task,
> which is place in ctx->errno. Then the coordinator wakes up and sees
> an -EINTR.
> 
> This patch changes the coordinator's behavior to report the error
> value placed in ctx->errno (if an error occurred) rather than report
> a confusing -EINTR.
> 
> Signed-off-by: Oren Laadan <orenl at cs.columbia.edu>

Acked-by: Serge Hallyn <serue at us.ibm.com>

> ---
>  checkpoint/restart.c |   15 +++++++++++++--
>  1 files changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/checkpoint/restart.c b/checkpoint/restart.c
> index 5daadc4..9b75de8 100644
> --- a/checkpoint/restart.c
> +++ b/checkpoint/restart.c
> @@ -711,7 +711,7 @@ static inline int is_task_active(struct ckpt_ctx *ctx, pid_t pid)
>  }
> 
>  /* should not be called under write_lock_irq(&tasklist_lock) */
> -static inline void _restore_notify_error(struct ckpt_ctx *ctx, int errno)
> +static void _restore_notify_error(struct ckpt_ctx *ctx, int errno)
>  {
>  	/* first to fail: notify everyone (racy but harmless) */
>  	if (!ckpt_test_ctx_error(ctx)) {
> @@ -1263,9 +1263,20 @@ static int do_restore_coord(struct ckpt_ctx *ctx, pid_t pid)
>  		post_restore_task();
> 
>  	restore_debug_error(ctx, ret);
> -	if (ret < 0) {
> +
> +	if (ret < 0)
>  		ckpt_set_ctx_error(ctx, ret);
> +
> +	if (ckpt_test_ctx_error(ctx)) {
>  		destroy_descendants(ctx);
> +		/*
> +		 * If a restaring task (or we) reported an error, that set
> +		 * out return value to that error. (Need the unlikely loop
> +		 * because the error is recorded after the flag is set).
> +		 */
> +		while (!ctx->errno)
> +			yield();
> +		ret = ctx->errno;
>  	} else {
>  		ckpt_set_ctx_success(ctx);
>  		wake_up_all(&ctx->waitq);
> -- 
> 1.6.0.4
> 
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