Re: [PATCH v2 2/3] md: add cond_resched() to md_do_sync()'s skip path

[yu kuai]

在 2026/7/23 21:55, Yunye Zhao 写道:

> When sync_request() reports a skipped region (*skipped == 1),
> md_do_sync()'s main loop advances the cursor and takes an early
> continue:
>
> 	j += sectors;
> 	...
> 	if (last_check + window > io_sectors || j == max_sectors)
> 		continue;
>
> If the personality returns a small span per call (raid10 recovery
> returns only 128 sectors), syncing a large, mostly clean array iterates
> this branch an enormous number of times without ever yielding the CPU.
> On a non-preemptive kernel the resync thread then trips the soft-lockup
> watchdog:
>
>    watchdog: BUG: soft lockup - CPU#149 stuck for 313s! [mdX_resync]
>     md_bitmap_start_sync+0x6f/0xe0
>     raid10_sync_request+0x2c9/0x1530 [raid10]
>     md_do_sync+0x810/0x1030
>     md_thread+0xa7/0x150
>
> Add a cond_resched().  This does not reduce the wasted iterations; the
> excessive iteration count is a raid10 problem addressed separately.
>
> Cc:stable@xxxxxxxxxxxxxxx
> Signed-off-by: Yunye Zhao<yunye.zhao@xxxxxxxxxxxxxxxxx>

Remove the cc stable as there is no fixtag.

> ---
>   drivers/md/md.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
Applied to md-7.3

-- 
Thanks,
Kuai