Dexuan Cui <decui@xxxxxxxxxxxxx> writes:
> In the case the user-space daemon crashes, hangs or is killed, we
> need to down the semaphore, otherwise, after the daemon starts next
> time, the obsolete data in fcopy_transaction.message or
> fcopy_transaction.fcopy_msg will be used immediately.
It seems this patch got lost and I don't see it in recent 'resend'
series. K.Y., Dexuan, can you please take a look?
>
> Cc: Jason Wang <jasowang@xxxxxxxxxx>
> Cc: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
> Cc: K. Y. Srinivasan <kys@xxxxxxxxxxxxx>
> Signed-off-by: Dexuan Cui <decui@xxxxxxxxxxxxx>
> ---
>
> v2: I removed the "FCP" prefix as Greg asked.
>
> I also updated the output message a little:
> "FCP: failed to acquire the semaphore" -->
> "can not acquire the semaphore: it is benign"
>
> v3: I added the code in fcopy_release() as Jason Wang suggested.
> I removed the pr_debug (it isn't so meaningful)and added a comment instead.
>
> drivers/hv/hv_fcopy.c | 19 +++++++++++++++++++
> 1 file changed, 19 insertions(+)
>
> diff --git a/drivers/hv/hv_fcopy.c b/drivers/hv/hv_fcopy.c
> index 23b2ce2..faa6ba6 100644
> --- a/drivers/hv/hv_fcopy.c
> +++ b/drivers/hv/hv_fcopy.c
> @@ -86,6 +86,18 @@ static void fcopy_work_func(struct work_struct *dummy)
> * process the pending transaction.
> */
> fcopy_respond_to_host(HV_E_FAIL);
> +
> + /* In the case the user-space daemon crashes, hangs or is killed, we
> + * need to down the semaphore, otherwise, after the daemon starts next
> + * time, the obsolete data in fcopy_transaction.message or
> + * fcopy_transaction.fcopy_msg will be used immediately.
> + *
> + * NOTE: fcopy_read() happens to get the semaphore (very rare)? We're
> + * still OK, because we've reported the failure to the host.
> + */
> + if (down_trylock(&fcopy_transaction.read_sema))
> + ;
> +
> }
>
> static int fcopy_handle_handshake(u32 version)
> @@ -351,6 +363,13 @@ static int fcopy_release(struct inode *inode, struct file *f)
> */
> in_hand_shake = true;
> opened = false;
> +
> + if (cancel_delayed_work_sync(&fcopy_work)) {
> + /* We haven't up()-ed the semaphore(very rare)? */
> + if (down_trylock(&fcopy_transaction.read_sema))
> + ;
> + fcopy_respond_to_host(HV_E_FAIL);
> + }
> return 0;
> }
--
Vitaly
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