[PATCH blktests] nvme/039: avoid failure by error message rate limit

[alan.adamson at oracle.com]

On 4/12/23 1:59 AM, Shin'ichiro Kawasaki wrote:
> From: Shin'ichiro Kawasaki <shinichiro.kawasaki at wdc.com>
>
> The test case nvme/039 tests that expected error messages are printed
> for errors injected to the nvme driver. However, the test case fails by
> chance when previous test cases generate many error messages. In this
> case, the kernel function pr_err_ratelimited() may suppress the error
> messages that the test case expects. Also, it may print messages that
> the test case does not expect, such as "blk_print_req_error: xxxx
> callbacks suppressed".
>
> To avoid the failure, make two improvements for the test case. Firstly,
> wait DEFAULT_RATE_LIMIT seconds at the beginning of the test to ensure
> the expected error messages are not suppressed. Secondly, exclude the
> unexpected message for the error message check. Introduce a helper
> function last_dmesg() for the second improvement.

Why are we seeing the callback messages?  By the time the test starts 
generating errors (after a 5 sec delay) we should be able to log 10 
messages without any being suppressed.

Alan