[v4,1/4] eventdev: fix race condition on timer list counter
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Commit Message
The n_poll_lcores counter and poll_lcore array are shared between lcores
and the update of these variables are out of the protection of spinlock
on each lcore timer list. The read-modify-write operations of the counter
are not atomic, so it has the potential of race condition between lcores.
Use c11 atomics with RELAXED ordering to prevent confliction.
Fixes: cc7b73ea9e3b ("eventdev: add new software timer adapter")
Cc: erik.g.carrillo@intel.com
Cc: stable@dpdk.org
Signed-off-by: Phil Yang <phil.yang@arm.com>
Reviewed-by: Dharmik Thakkar <dharmik.thakkar@arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
Acked-by: Erik Gabriel Carrillo <erik.g.carrillo@intel.com>
---
v2:
Align the code. (Erik)
lib/librte_eventdev/rte_event_timer_adapter.c | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)
Comments
On Tue, Jul 7, 2020 at 9:25 PM Phil Yang <phil.yang@arm.com> wrote:
>
> The n_poll_lcores counter and poll_lcore array are shared between lcores
> and the update of these variables are out of the protection of spinlock
> on each lcore timer list. The read-modify-write operations of the counter
> are not atomic, so it has the potential of race condition between lcores.
>
> Use c11 atomics with RELAXED ordering to prevent confliction.
>
> Fixes: cc7b73ea9e3b ("eventdev: add new software timer adapter")
> Cc: erik.g.carrillo@intel.com
> Cc: stable@dpdk.org
>
> Signed-off-by: Phil Yang <phil.yang@arm.com>
> Reviewed-by: Dharmik Thakkar <dharmik.thakkar@arm.com>
> Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
> Acked-by: Erik Gabriel Carrillo <erik.g.carrillo@intel.com>
Hi Thomas,
The latest version does not have ABI breakage issue.
I have added the ABI verifier in my local patch verification setup.
Series applied to dpdk-next-eventdev/master.
Please pull this series from dpdk-next-eventdev/master. Thanks.
I am marking this patch series as "Awaiting Upstream" in patchwork
status to reflect the actual status.
08/07/2020 15:30, Jerin Jacob:
> On Tue, Jul 7, 2020 at 9:25 PM Phil Yang <phil.yang@arm.com> wrote:
> >
> > The n_poll_lcores counter and poll_lcore array are shared between lcores
> > and the update of these variables are out of the protection of spinlock
> > on each lcore timer list. The read-modify-write operations of the counter
> > are not atomic, so it has the potential of race condition between lcores.
> >
> > Use c11 atomics with RELAXED ordering to prevent confliction.
> >
> > Fixes: cc7b73ea9e3b ("eventdev: add new software timer adapter")
> > Cc: erik.g.carrillo@intel.com
> > Cc: stable@dpdk.org
> >
> > Signed-off-by: Phil Yang <phil.yang@arm.com>
> > Reviewed-by: Dharmik Thakkar <dharmik.thakkar@arm.com>
> > Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
> > Acked-by: Erik Gabriel Carrillo <erik.g.carrillo@intel.com>
>
> Hi Thomas,
>
> The latest version does not have ABI breakage issue.
>
> I have added the ABI verifier in my local patch verification setup.
>
> Series applied to dpdk-next-eventdev/master.
>
> Please pull this series from dpdk-next-eventdev/master. Thanks.
>
> I am marking this patch series as "Awaiting Upstream" in patchwork
> status to reflect the actual status.
OK, pulled and marked as Accepted in patchwork.
@@ -583,6 +583,7 @@ swtim_callback(struct rte_timer *tim)
uint16_t nb_evs_invalid = 0;
uint64_t opaque;
int ret;
+ int n_lcores;
opaque = evtim->impl_opaque[1];
adapter = (struct rte_event_timer_adapter *)(uintptr_t)opaque;
@@ -605,8 +606,12 @@ swtim_callback(struct rte_timer *tim)
"with immediate expiry value");
}
- if (unlikely(rte_atomic16_test_and_set(&sw->in_use[lcore].v)))
- sw->poll_lcores[sw->n_poll_lcores++] = lcore;
+ if (unlikely(rte_atomic16_test_and_set(&sw->in_use[lcore].v))) {
+ n_lcores = __atomic_fetch_add(&sw->n_poll_lcores, 1,
+ __ATOMIC_RELAXED);
+ __atomic_store_n(&sw->poll_lcores[n_lcores], lcore,
+ __ATOMIC_RELAXED);
+ }
} else {
EVTIM_BUF_LOG_DBG("buffered an event timer expiry event");
@@ -1011,6 +1016,7 @@ __swtim_arm_burst(const struct rte_event_timer_adapter *adapter,
uint32_t lcore_id = rte_lcore_id();
struct rte_timer *tim, *tims[nb_evtims];
uint64_t cycles;
+ int n_lcores;
#ifdef RTE_LIBRTE_EVENTDEV_DEBUG
/* Check that the service is running. */
@@ -1033,8 +1039,10 @@ __swtim_arm_burst(const struct rte_event_timer_adapter *adapter,
if (unlikely(rte_atomic16_test_and_set(&sw->in_use[lcore_id].v))) {
EVTIM_LOG_DBG("Adding lcore id = %u to list of lcores to poll",
lcore_id);
- sw->poll_lcores[sw->n_poll_lcores] = lcore_id;
- ++sw->n_poll_lcores;
+ n_lcores = __atomic_fetch_add(&sw->n_poll_lcores, 1,
+ __ATOMIC_RELAXED);
+ __atomic_store_n(&sw->poll_lcores[n_lcores], lcore_id,
+ __ATOMIC_RELAXED);
}
ret = rte_mempool_get_bulk(sw->tim_pool, (void **)tims,