Re: [PATCH net-next v2 2/2] net/smc: reduce TX slot contention with exclusive wait

> smc_wr_tx_get_free_slot() waits for a free TX slot with
> wait_event_interruptible_timeout(). Since the wait_event family
> enqueues waiters as non-exclusive, wake_up() may wake multiple
> waiters even though only one can use the slot, causing
> thundering-herd contention when slots are scarce.
> 
> Use an exclusive wait loop with prepare_to_wait_exclusive() so
> wake_up() wakes only one waiter per freed slot.
> smc_wr_wakeup_tx_wait() still uses wake_up_all() during link
> teardown, so teardown behavior is unchanged.
> 
> This also corrects the return value on a pending signal: the previous
> wait_event_interruptible_timeout() path fell through to the "no free
> slot" case and returned -EPIPE, masking the signal as a connection
> error. The open-coded loop now returns -ERESTARTSYS, matching the
> [ ... ]
> So the change does not regress the uncontended case, and recovers most
> of the throughput lost to thundering-herd wakeups once slots become
> scarce.
> 
> Signed-off-by: D. Wythe <[email protected]>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=2