Re: [PATCH net 3/3] net/smc: Resolve the race between SMC-R link access and clear

Karsten Graul
2022-01-11T08:40:18Z

On 10/01/2022 10:26, Wen Gu wrote:
> @@ -1226,15 +1245,23 @@ void smcr_link_clear(struct smc_link *lnk, bool log)
> smc_wr_free_link(lnk);
> smc_ib_destroy_queue_pair(lnk);
> smc_ib_dealloc_protection_domain(lnk);
> - smc_wr_free_link_mem(lnk);
> - smc_lgr_put(lnk->lgr); /* lgr_hold in smcr_link_init() */
> smc_ibdev_cnt_dec(lnk);
> put_device(&lnk->smcibdev->ibdev->dev);
> smcibdev = lnk->smcibdev;
> - memset(lnk, 0, sizeof(struct smc_link));
> - lnk->state = SMC_LNK_UNUSED;
> if (!atomic_dec_return(&smcibdev->lnk_cnt))
> wake_up(&smcibdev->lnks_deleted);

Same here, waiter should not be woken up until the link memory is actually freed.

> + smcr_link_put(lnk); /* theoretically last link_put */
> +}
> +
> +void smcr_link_hold(struct smc_link *lnk)
> +{
> + refcount_inc(&lnk->refcnt);
> +}
> +
> +void smcr_link_put(struct smc_link *lnk)
> +{
> + if (refcount_dec_and_test(&lnk->refcnt))
> + __smcr_link_clear(lnk);
> }