[dm-devel] [PATCH 12/12] multipathd: marginal path code fixes

[Martin Wilck]

On Thu, 2017-12-07 at 12:49 -0600, Benjamin Marzinski wrote:
> There are a couple of issues I noticed with the marginal paths code.
> 
> In hit_io_err_recheck_time() there are some problems with the initial
> checks. We should always recover the path if there are no other
> usable
> paths to the device, so this check should be first. Also, we just
> checked that io_err_disable_reinstate isn't zero before calling this
> function, so we don't need to check again here (and it doesn't make
> any
> sense to continue disabling the path if io_err_disable_reinstate is
> set
> to zero).  Finally, the only kind of errors we can get while calling
> clock_gettime() are going to happen on every call. So, if we can't
> get
> the time, assume that the timeout has passed.
> 
> The multipath.conf.5 description of marginal_path_err_sample_time,
> states that sampling is stopped for marginal_path_err_rate_threshold
> seconds, when it should be marginal_path_err_recheck_gap_time
> seconds.
> 
> Lastly, there is a race that can cause multipathd to access freed
> memory
> on shutdown. io_err_stat_thr is started as a detached thread. This
> means
> that stop_io_err_stat_thread() can't know when it has actually
> stopped,
> after pthread_cancel() and pthread_kill() are called. To be safe, it
> should not start the thread in a deteched state, and call join to
> verify
> that it has stopped before freeing the memory it uses.  But more
> importantly, stop_io_err_stat_thread() was being called before the
> checker and uevent threads were being canceled. Both of these threads
> access data that is freed in stop_io_err_stat_thread(). To avoid the
> chance of these threads accessing freed memory, child() should wait
> until these threads are stopped before calling
> stop_io_err_stat_thread().
> 
> Cc: Guan Junxiong <guanjunxiong at huawei.com>
> Signed-off-by: Benjamin Marzinski <bmarzins at redhat.com>
> ---

Reviewed-by: Martin Wilck <mwilck at suse.com>

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