[v8,01/17] distributor: fix missing handshake synchronization
diff mbox series

Message ID 20201017030701.16134-2-l.wojciechow@partner.samsung.com
State Accepted
Delegated to: David Marchand
Headers show
Series
  • fix distributor synchronization issues
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Checks

Context Check Description
ci/checkpatch success coding style OK

Commit Message

Lukasz Wojciechowski Oct. 17, 2020, 3:06 a.m. UTC
rte_distributor_return_pkt function which is run on worker cores
must wait for distributor core to clear handshake on retptr64
before using those buffers. While the handshake is set distributor
core controls buffers and any operations on worker side might overwrite
buffers which are unread yet.
Same situation appears in the legacy single distributor. Function
rte_distributor_return_pkt_single shouldn't modify the bufptr64 until
handshake on it is cleared by distributor lcore.

Fixes: 775003ad2f96 ("distributor: add new burst-capable library")
Cc: david.hunt@intel.com
Cc: stable@dpdk.org

Signed-off-by: Lukasz Wojciechowski <l.wojciechow@partner.samsung.com>
Acked-by: David Hunt <david.hunt@intel.com>
---
 lib/librte_distributor/rte_distributor.c        | 12 ++++++++++++
 lib/librte_distributor/rte_distributor_single.c |  4 ++++
 2 files changed, 16 insertions(+)

Comments

Honnappa Nagarahalli Oct. 17, 2020, 9:05 p.m. UTC | #1
<snip>
> 
> rte_distributor_return_pkt function which is run on worker cores must wait
> for distributor core to clear handshake on retptr64 before using those
> buffers. While the handshake is set distributor core controls buffers and any
> operations on worker side might overwrite buffers which are unread yet.
> Same situation appears in the legacy single distributor. Function
> rte_distributor_return_pkt_single shouldn't modify the bufptr64 until
> handshake on it is cleared by distributor lcore.
> 
> Fixes: 775003ad2f96 ("distributor: add new burst-capable library")
> Cc: david.hunt@intel.com
> Cc: stable@dpdk.org
> 
> Signed-off-by: Lukasz Wojciechowski <l.wojciechow@partner.samsung.com>
> Acked-by: David Hunt <david.hunt@intel.com>
Looks good.
Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>

> ---
>  lib/librte_distributor/rte_distributor.c        | 12 ++++++++++++
>  lib/librte_distributor/rte_distributor_single.c |  4 ++++
>  2 files changed, 16 insertions(+)
> 
> diff --git a/lib/librte_distributor/rte_distributor.c
> b/lib/librte_distributor/rte_distributor.c
> index 1c047f065..c6b19a388 100644
> --- a/lib/librte_distributor/rte_distributor.c
> +++ b/lib/librte_distributor/rte_distributor.c
> @@ -169,6 +169,18 @@ rte_distributor_return_pkt(struct rte_distributor *d,
>  			return -EINVAL;
>  	}
> 
> +	/* Spin while handshake bits are set (scheduler clears it).
> +	 * Sync with worker on GET_BUF flag.
> +	 */
> +	while (unlikely(__atomic_load_n(&(buf->retptr64[0]),
> __ATOMIC_RELAXED)
> +			& RTE_DISTRIB_GET_BUF)) {
> +		rte_pause();
> +		uint64_t t = rte_rdtsc()+100;
> +
> +		while (rte_rdtsc() < t)
> +			rte_pause();
> +	}
> +
>  	/* Sync with distributor to acquire retptrs */
>  	__atomic_thread_fence(__ATOMIC_ACQUIRE);
>  	for (i = 0; i < RTE_DIST_BURST_SIZE; i++) diff --git
> a/lib/librte_distributor/rte_distributor_single.c
> b/lib/librte_distributor/rte_distributor_single.c
> index abaf7730c..f4725b1d0 100644
> --- a/lib/librte_distributor/rte_distributor_single.c
> +++ b/lib/librte_distributor/rte_distributor_single.c
> @@ -74,6 +74,10 @@ rte_distributor_return_pkt_single(struct
> rte_distributor_single *d,
>  	union rte_distributor_buffer_single *buf = &d->bufs[worker_id];
>  	uint64_t req = (((int64_t)(uintptr_t)oldpkt) <<
> RTE_DISTRIB_FLAG_BITS)
>  			| RTE_DISTRIB_RETURN_BUF;
> +	while (unlikely(__atomic_load_n(&buf->bufptr64,
> __ATOMIC_RELAXED)
> +			& RTE_DISTRIB_FLAGS_MASK))
> +		rte_pause();
> +
>  	/* Sync with distributor on RETURN_BUF flag. */
>  	__atomic_store_n(&(buf->bufptr64), req, __ATOMIC_RELEASE);
>  	return 0;
> --
> 2.17.1

Patch
diff mbox series

diff --git a/lib/librte_distributor/rte_distributor.c b/lib/librte_distributor/rte_distributor.c
index 1c047f065..c6b19a388 100644
--- a/lib/librte_distributor/rte_distributor.c
+++ b/lib/librte_distributor/rte_distributor.c
@@ -169,6 +169,18 @@  rte_distributor_return_pkt(struct rte_distributor *d,
 			return -EINVAL;
 	}
 
+	/* Spin while handshake bits are set (scheduler clears it).
+	 * Sync with worker on GET_BUF flag.
+	 */
+	while (unlikely(__atomic_load_n(&(buf->retptr64[0]), __ATOMIC_RELAXED)
+			& RTE_DISTRIB_GET_BUF)) {
+		rte_pause();
+		uint64_t t = rte_rdtsc()+100;
+
+		while (rte_rdtsc() < t)
+			rte_pause();
+	}
+
 	/* Sync with distributor to acquire retptrs */
 	__atomic_thread_fence(__ATOMIC_ACQUIRE);
 	for (i = 0; i < RTE_DIST_BURST_SIZE; i++)
diff --git a/lib/librte_distributor/rte_distributor_single.c b/lib/librte_distributor/rte_distributor_single.c
index abaf7730c..f4725b1d0 100644
--- a/lib/librte_distributor/rte_distributor_single.c
+++ b/lib/librte_distributor/rte_distributor_single.c
@@ -74,6 +74,10 @@  rte_distributor_return_pkt_single(struct rte_distributor_single *d,
 	union rte_distributor_buffer_single *buf = &d->bufs[worker_id];
 	uint64_t req = (((int64_t)(uintptr_t)oldpkt) << RTE_DISTRIB_FLAG_BITS)
 			| RTE_DISTRIB_RETURN_BUF;
+	while (unlikely(__atomic_load_n(&buf->bufptr64, __ATOMIC_RELAXED)
+			& RTE_DISTRIB_FLAGS_MASK))
+		rte_pause();
+
 	/* Sync with distributor on RETURN_BUF flag. */
 	__atomic_store_n(&(buf->bufptr64), req, __ATOMIC_RELEASE);
 	return 0;