Hi Michal,
> -----Original Message-----
> From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Michal Jastrzebski
> Sent: Tuesday, September 23, 2014 4:02 PM
> To: dev at dpdk.org
> Subject: [dpdk-dev] [PATCH] Change alarm cancel function to thread-safe.
>
> It eliminates a race between threads using rte_alarm_cancel and rte_alarm_set.
>
> Signed-off-by: Pawel Wodkowski <pawelx.wodkowski at intel.com>
> Reviewed-by: Michal Jastrzebski <michalx.k.jastrzebski at intel.com>
The patch looks good, but I think it is incomplete.
At rte_eal_alarm_set(), for newly allocated alarm_entry we never reset value of
'executing' to zero.
Yes, it seems that problem is not new, and was here for a while.
Probably the easiest way to fix it:
@@ -150,7 +150,7 @@ rte_eal_alarm_set(uint64_t us, rte_eal_alarm_callback
cb_fn, void *cb_arg)
if (us < 1 || us > (UINT64_MAX - US_PER_S) || cb_fn == NULL)
return -EINVAL;
- new_alarm = rte_malloc(NULL, sizeof(*new_alarm), 0);
+ new_alarm = rte_zmalloc(NULL, sizeof(*new_alarm), 0);
if (new_alarm == NULL)
return -ENOMEM;
Plus two nits, see below.
Thanks
Konstantin
> ---
> lib/librte_eal/common/include/rte_alarm.h | 3 +-
> lib/librte_eal/linuxapp/eal/eal_alarm.c | 68
> +++++++++++++++++++----------
> 2 files changed, 46 insertions(+), 25 deletions(-)
>
> diff --git a/lib/librte_eal/common/include/rte_alarm.h
> b/lib/librte_eal/common/include/rte_alarm.h
> index d451522..f5f7de4 100644
> --- a/lib/librte_eal/common/include/rte_alarm.h
> +++ b/lib/librte_eal/common/include/rte_alarm.h
> @@ -76,7 +76,8 @@ typedef void (*rte_eal_alarm_callback)(void *arg);
> int rte_eal_alarm_set(uint64_t us, rte_eal_alarm_callback cb, void *cb_arg);
>
> /**
> - * Function to cancel an alarm callback which has been registered before.
> + * Function to cancel an alarm callback which has been registered before. If
> + * used ouside alarm callback it wait for all callbacks to finish its
> execution.
s/ouside/outside/
> *
> * @param cb_fn
> * alarm callback
> diff --git a/lib/librte_eal/linuxapp/eal/eal_alarm.c
> b/lib/librte_eal/linuxapp/eal/eal_alarm.c
> index 480f0cb..0561dbf 100644
> --- a/lib/librte_eal/linuxapp/eal/eal_alarm.c
> +++ b/lib/librte_eal/linuxapp/eal/eal_alarm.c
> @@ -69,12 +69,14 @@ struct alarm_entry {
> struct timeval time;
> rte_eal_alarm_callback cb_fn;
> void *cb_arg;
> - volatile int executing;
> + volatile uint8_t executing;
> + volatile pthread_t executing_id;
> };
>
> static LIST_HEAD(alarm_list, alarm_entry) alarm_list =
> LIST_HEAD_INITIALIZER();
> static rte_spinlock_t alarm_list_lk = RTE_SPINLOCK_INITIALIZER;
>
> +
> static struct rte_intr_handle intr_handle = {.fd = -1 };
> static int handler_registered = 0;
> static void eal_alarm_callback(struct rte_intr_handle *hdl, void *arg);
> @@ -108,11 +110,14 @@ eal_alarm_callback(struct rte_intr_handle *hdl
> __rte_unused,
> (ap->time.tv_sec < now.tv_sec || (ap->time.tv_sec ==
> now.tv_sec &&
> ap->time.tv_usec <=
> now.tv_usec))){
> ap->executing = 1;
> + ap->executing_id = pthread_self();
> rte_spinlock_unlock(&alarm_list_lk);
>
> ap->cb_fn(ap->cb_arg);
>
> rte_spinlock_lock(&alarm_list_lk);
> + ap->executing = 0;
> +
I don't think you need:
ap->executing = 0
here.
You are going to free ap anyway.
> LIST_REMOVE(ap, next);
> rte_free(ap);
> }
> @@ -156,7 +161,6 @@ rte_eal_alarm_set(uint64_t us, rte_eal_alarm_callback
> cb_fn, void *cb_arg)
> new_alarm->cb_arg = cb_arg;
> new_alarm->time.tv_usec = (now.tv_usec + us) % US_PER_S;
> new_alarm->time.tv_sec = now.tv_sec + ((now.tv_usec + us) / US_PER_S);
> - new_alarm->executing = 0;
>
> rte_spinlock_lock(&alarm_list_lk);
> if (!handler_registered) {
> @@ -202,34 +206,50 @@ rte_eal_alarm_cancel(rte_eal_alarm_callback cb_fn, void
> *cb_arg)
> {
> struct alarm_entry *ap, *ap_prev;
> int count = 0;
> + int executing;
>
> if (!cb_fn)
> return -1;
>
> - rte_spinlock_lock(&alarm_list_lk);
> - /* remove any matches at the start of the list */
> - while ((ap = LIST_FIRST(&alarm_list)) != NULL &&
> - cb_fn == ap->cb_fn && ap->executing == 0 &&
> - (cb_arg == (void *)-1 || cb_arg == ap->cb_arg)) {
> - LIST_REMOVE(ap, next);
> - rte_free(ap);
> - count++;
> - }
> - ap_prev = ap;
> -
> - /* now go through list, removing entries not at start */
> - LIST_FOREACH(ap, &alarm_list, next) {
> - /* this won't be true first time through */
> - if (cb_fn == ap->cb_fn && ap->executing == 0 &&
> + do {
> + executing = 0;
> + rte_spinlock_lock(&alarm_list_lk);
> + /* remove any matches at the start of the list */
> + while ((ap = LIST_FIRST(&alarm_list)) != NULL &&
> + cb_fn == ap->cb_fn &&
> (cb_arg == (void *)-1 || cb_arg == ap->cb_arg))
> {
> - LIST_REMOVE(ap,next);
> - rte_free(ap);
> - count++;
> - ap = ap_prev;
> +
> + if (ap->executing == 0) {
> + LIST_REMOVE(ap, next);
> + rte_free(ap);
> + count++;
> + } else {
> + if (pthread_equal(ap->executing_id,
> pthread_self()) == 0)
> + executing++;
> +
> + break;
> + }
> }
> ap_prev = ap;
> - }
> - rte_spinlock_unlock(&alarm_list_lk);
> +
> + /* now go through list, removing entries not at start */
> + LIST_FOREACH(ap, &alarm_list, next) {
> + /* this won't be true first time through */
> + if (cb_fn == ap->cb_fn &&
> + (cb_arg == (void *)-1 || cb_arg ==
> ap->cb_arg)) {
> +
> + if (ap->executing == 0) {
> + LIST_REMOVE(ap, next);
> + rte_free(ap);
> + count++;
> + ap = ap_prev;
> + } else if (pthread_equal(ap->executing_id,
> pthread_self()) == 0)
> + executing++;
> + }
> + ap_prev = ap;
> + }
> + rte_spinlock_unlock(&alarm_list_lk);
> + } while (executing != 0);
> +
> return count;
> }
> -
> --
> 1.7.9.5
