[dpdk-dev] [PATCH v5 4/5] lib/bpf: use wait event scheme for Rx/Tx iteration

[Feifei Wang]

Instead of polling for cbi->use to be updated, use wait event scheme.

Furthermore, delete 'const' for 'bpf_eth_cbi_wait'. This is because of
a compilation error:
-----------------------------------------------------------------------
../lib/eal/include/rte_common.h:36:13: error: read-only variable ‘value’
used as ‘asm’ output
   36 | #define asm __asm__
      |             ^~~~~~~

../lib/eal/arm/include/rte_pause_64.h:66:3: note: in expansion of macro
‘asm’
   66 |   asm volatile("ldaxr %w[tmp], [%x[addr]]" \
      |   ^~~

../lib/eal/arm/include/rte_pause_64.h:96:3: note: in expansion of macro
‘__LOAD_EXC_32’
   96 |   __LOAD_EXC_32((src), dst, memorder)     \
      |   ^~~~~~~~~~~~~

../lib/eal/arm/include/rte_pause_64.h:167:4: note: in expansion of macro
‘__LOAD_EXC’
  167 |    __LOAD_EXC((addr), value, memorder, size) \
      |    ^~~~~~~~~~

../lib/bpf/bpf_pkt.c:125:3: note: in expansion of macro ‘rte_wait_event’
  125 |   rte_wait_event(&cbi->use, UINT32_MAX, ==, puse,
-----------------------------------------------------------------------

Signed-off-by: Feifei Wang <feifei.wang2 at arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang at arm.com>
---
 lib/bpf/bpf_pkt.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/lib/bpf/bpf_pkt.c b/lib/bpf/bpf_pkt.c
index 6e8248f0d6..213d44a75a 100644
--- a/lib/bpf/bpf_pkt.c
+++ b/lib/bpf/bpf_pkt.c
@@ -111,9 +111,9 @@ bpf_eth_cbi_unuse(struct bpf_eth_cbi *cbi)
  * Waits till datapath finished using given callback.
  */
 static void
-bpf_eth_cbi_wait(const struct bpf_eth_cbi *cbi)
+bpf_eth_cbi_wait(struct bpf_eth_cbi *cbi)
 {
-	uint32_t nuse, puse;
+	uint32_t puse;
 
 	/* make sure all previous loads and stores are completed */
 	rte_smp_mb();
@@ -122,11 +122,8 @@ bpf_eth_cbi_wait(const struct bpf_eth_cbi *cbi)
 
 	/* in use, busy wait till current RX/TX iteration is finished */
 	if ((puse & BPF_ETH_CBI_INUSE) != 0) {
-		do {
-			rte_pause();
-			rte_compiler_barrier();
-			nuse = cbi->use;
-		} while (nuse == puse);
+		rte_wait_event(&cbi->use, UINT32_MAX, ==, puse,
+				__ATOMIC_RELAXED);
 	}
 }
 
-- 
2.25.1