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References: <20230124160945.3003303-1-erik.g.carrillo@intel.com>
<20230124204555.3022361-1-erik.g.carrillo@intel.com>
In-Reply-To: <20230124204555.3022361-1-erik.g.carrillo@intel.com>
From: Jerin Jacob <jerinjacobk@gmail.com>
Date: Tue, 7 Feb 2023 11:30:33 +0530
Message-ID: <CALBAE1PaWLhXU=1AAFDHNu1hqnE3w1e6GL2XE1i0vSU6cVf3iw@mail.gmail.com>
Subject: Re: [PATCH v2] eventdev/timer: fix overflow issue
To: Erik Gabriel Carrillo <erik.g.carrillo@intel.com>,
Stephen Hemminger <stephen@networkplumber.org>
Cc: jerinj@marvell.com, dev@dpdk.org, stable@dpdk.org
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On Wed, Jan 25, 2023 at 2:16 AM Erik Gabriel Carrillo
<erik.g.carrillo@intel.com> wrote:
>
> The software timer adapter converts event timer timeout ticks to a
> number of CPU cycles at which an rte_timer should expire. The
> computation uses integer operations that can result in overflow.
>
> Use floating point operations instead to perform the computation, and
> convert the final result back to an integer type when returning. Also
> move the logic that checks the timeout range into the function that
> performs the above computation.
>
> Fixes: 6750b21bd6af ("eventdev: add default software timer adapter")
> Cc: stable@dpdk.org
>
> Signed-off-by: Erik Gabriel Carrillo <erik.g.carrillo@intel.com>
> ---
> v2:
> * Fix implicit int to float conversion build warning on Clang
Not yet addressed the @Stephen Hemminger comments on using of
rte_reciprocal. Also means to check what compute can be moved to
slowpath.
Marking as "Change requested", Looking for next version.
>
> lib/eventdev/rte_event_timer_adapter.c | 71 ++++++++++++--------------
> 1 file changed, 34 insertions(+), 37 deletions(-)
>
> diff --git a/lib/eventdev/rte_event_timer_adapter.c b/lib/eventdev/rte_event_timer_adapter.c
> index d357f7403a..2efeb73bce 100644
> --- a/lib/eventdev/rte_event_timer_adapter.c
> +++ b/lib/eventdev/rte_event_timer_adapter.c
> @@ -719,13 +719,28 @@ swtim_callback(struct rte_timer *tim)
> }
> }
>
> -static __rte_always_inline uint64_t
> +static __rte_always_inline int
> get_timeout_cycles(struct rte_event_timer *evtim,
> - const struct rte_event_timer_adapter *adapter)
> + const struct rte_event_timer_adapter *adapter,
> + uint64_t *timeout_cycles)
> {
> struct swtim *sw = swtim_pmd_priv(adapter);
> - uint64_t timeout_ns = evtim->timeout_ticks * sw->timer_tick_ns;
> - return timeout_ns * rte_get_timer_hz() / NSECPERSEC;
> + uint64_t timeout_nsecs;
> + double cycles_per_nsec;
> +
> + cycles_per_nsec = (double)rte_get_timer_hz() / NSECPERSEC;
> +
> + timeout_nsecs = evtim->timeout_ticks * sw->timer_tick_ns;
> + if (timeout_nsecs > sw->max_tmo_ns)
> + return -1;
> + if (timeout_nsecs < sw->timer_tick_ns)
> + return -2;
> +
> + if (timeout_cycles)
> + *timeout_cycles = (uint64_t)ceil(timeout_nsecs *
> + cycles_per_nsec);
> +
> + return 0;
> }
>
> /* This function returns true if one or more (adapter) ticks have occurred since
> @@ -759,23 +774,6 @@ swtim_did_tick(struct swtim *sw)
> return false;
> }
>
> -/* Check that event timer timeout value is in range */
> -static __rte_always_inline int
> -check_timeout(struct rte_event_timer *evtim,
> - const struct rte_event_timer_adapter *adapter)
> -{
> - uint64_t tmo_nsec;
> - struct swtim *sw = swtim_pmd_priv(adapter);
> -
> - tmo_nsec = evtim->timeout_ticks * sw->timer_tick_ns;
> - if (tmo_nsec > sw->max_tmo_ns)
> - return -1;
> - if (tmo_nsec < sw->timer_tick_ns)
> - return -2;
> -
> - return 0;
> -}
> -
> /* Check that event timer event queue sched type matches destination event queue
> * sched type
> */
> @@ -1195,21 +1193,6 @@ __swtim_arm_burst(const struct rte_event_timer_adapter *adapter,
> break;
> }
>
> - ret = check_timeout(evtims[i], adapter);
> - if (unlikely(ret == -1)) {
> - __atomic_store_n(&evtims[i]->state,
> - RTE_EVENT_TIMER_ERROR_TOOLATE,
> - __ATOMIC_RELAXED);
> - rte_errno = EINVAL;
> - break;
> - } else if (unlikely(ret == -2)) {
> - __atomic_store_n(&evtims[i]->state,
> - RTE_EVENT_TIMER_ERROR_TOOEARLY,
> - __ATOMIC_RELAXED);
> - rte_errno = EINVAL;
> - break;
> - }
> -
> if (unlikely(check_destination_event_queue(evtims[i],
> adapter) < 0)) {
> __atomic_store_n(&evtims[i]->state,
> @@ -1225,7 +1208,21 @@ __swtim_arm_burst(const struct rte_event_timer_adapter *adapter,
> evtims[i]->impl_opaque[0] = (uintptr_t)tim;
> evtims[i]->impl_opaque[1] = (uintptr_t)adapter;
>
> - cycles = get_timeout_cycles(evtims[i], adapter);
> + ret = get_timeout_cycles(evtims[i], adapter, &cycles);
> + if (unlikely(ret == -1)) {
> + __atomic_store_n(&evtims[i]->state,
> + RTE_EVENT_TIMER_ERROR_TOOLATE,
> + __ATOMIC_RELAXED);
> + rte_errno = EINVAL;
> + break;
> + } else if (unlikely(ret == -2)) {
> + __atomic_store_n(&evtims[i]->state,
> + RTE_EVENT_TIMER_ERROR_TOOEARLY,
> + __ATOMIC_RELAXED);
> + rte_errno = EINVAL;
> + break;
> + }
> +
> ret = rte_timer_alt_reset(sw->timer_data_id, tim, cycles,
> type, lcore_id, NULL, evtims[i]);
> if (ret < 0) {
> --
> 2.23.0
>