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Re: [PATCH 1/2] hyperv: Use auto rcu_read macros
From: |
Roman Kagan |
Subject: |
Re: [PATCH 1/2] hyperv: Use auto rcu_read macros |
Date: |
Fri, 13 Dec 2019 13:58:52 +0000 |
On Fri, Dec 13, 2019 at 01:19:30PM +0000, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <address@hidden>
>
> Use RCU_READ_LOCK_GUARD and WITH_RCU_READ_LOCK_GUARD
> to replace the manual rcu_read_(un)lock calls.
>
> Signed-off-by: Dr. David Alan Gilbert <address@hidden>
> ---
> hw/hyperv/hyperv.c | 22 +++++++++-------------
> 1 file changed, 9 insertions(+), 13 deletions(-)
>
> diff --git a/hw/hyperv/hyperv.c b/hw/hyperv/hyperv.c
> index 6ebf31c310..da8ce82725 100644
> --- a/hw/hyperv/hyperv.c
> +++ b/hw/hyperv/hyperv.c
> @@ -546,14 +546,14 @@ uint16_t hyperv_hcall_post_message(uint64_t param, bool
> fast)
> }
>
> ret = HV_STATUS_INVALID_CONNECTION_ID;
> - rcu_read_lock();
> - QLIST_FOREACH_RCU(mh, &msg_handlers, link) {
> - if (mh->conn_id == (msg->connection_id & HV_CONNECTION_ID_MASK)) {
> - ret = mh->handler(msg, mh->data);
> - break;
> + WITH_RCU_READ_LOCK_GUARD() {
> + QLIST_FOREACH_RCU(mh, &msg_handlers, link) {
> + if (mh->conn_id == (msg->connection_id & HV_CONNECTION_ID_MASK))
> {
> + ret = mh->handler(msg, mh->data);
> + break;
> + }
> }
> }
> - rcu_read_unlock();
>
> unmap:
> cpu_physical_memory_unmap(msg, len, 0, 0);
> @@ -619,7 +619,6 @@ int hyperv_set_event_flag_handler(uint32_t conn_id,
> EventNotifier *notifier)
>
> uint16_t hyperv_hcall_signal_event(uint64_t param, bool fast)
> {
> - uint16_t ret;
> EventFlagHandler *handler;
>
> if (unlikely(!fast)) {
> @@ -645,15 +644,12 @@ uint16_t hyperv_hcall_signal_event(uint64_t param, bool
> fast)
> return HV_STATUS_INVALID_HYPERCALL_INPUT;
> }
>
> - ret = HV_STATUS_INVALID_CONNECTION_ID;
> - rcu_read_lock();
> + RCU_READ_LOCK_GUARD();
> QLIST_FOREACH_RCU(handler, &event_flag_handlers, link) {
> if (handler->conn_id == param) {
> event_notifier_set(handler->notifier);
> - ret = 0;
> - break;
> + return 0;
> }
> }
> - rcu_read_unlock();
> - return ret;
> + return HV_STATUS_INVALID_CONNECTION_ID;
> }
I have a slight preference towards using WITH_RCU_READ_LOCK_GUARD
instead of sticking RCU_READ_LOCK_GUARD in the middle of the function
and implicitly relying on there being none but trivial statements past
the rcu-protected section.
Nothing that I would insist on, though, so
Reviewed-by: Roman Kagan <address@hidden>