diff mbox series

[net,v2] selftests/net: toeplitz: fix race on tpacket_v3 block close

Message ID 20230118151847.4124260-1-willemdebruijn.kernel@gmail.com (mailing list archive)
State Accepted
Commit 903848249a781d76d59561d51676c95b3a4d7162
Delegated to: Netdev Maintainers
Headers show
Series [net,v2] selftests/net: toeplitz: fix race on tpacket_v3 block close | expand

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Context Check Description
netdev/tree_selection success Clearly marked for net
netdev/fixes_present success Fixes tag present in non-next series
netdev/subject_prefix success Link
netdev/cover_letter success Single patches do not need cover letters
netdev/patch_count success Link
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 0 this patch: 0
netdev/cc_maintainers fail 1 blamed authors not CCed: lixiaoyan@google.com; 3 maintainers not CCed: lixiaoyan@google.com linux-kselftest@vger.kernel.org shuah@kernel.org
netdev/build_clang success Errors and warnings before: 0 this patch: 0
netdev/module_param success Was 0 now: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success Fixes tag looks correct
netdev/build_allmodconfig_warn success Errors and warnings before: 0 this patch: 0
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 46 lines checked
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0

Commit Message

Willem de Bruijn Jan. 18, 2023, 3:18 p.m. UTC 
From: Willem de Bruijn <willemb@google.com>

Avoid race between process wakeup and tpacket_v3 block timeout.

The test waits for cfg_timeout_msec for packets to arrive. Packets
arrive in tpacket_v3 rings, which pass packets ("frames") to the
process in batches ("blocks"). The sk waits for req3.tp_retire_blk_tov
msec to release a block.

Set the block timeout lower than the process waiting time, else
the process may find that no block has been released by the time it
scans the socket list. Convert to a ring of more than one, smaller,
blocks with shorter timeouts. Blocks must be page aligned, so >= 64KB.

Fixes: 5ebfb4cc3048 ("selftests/net: toeplitz test")
Signed-off-by: Willem de Bruijn <willemb@google.com>

---

v1->v2: replace while with ; on next line with single-line do while
---
 tools/testing/selftests/net/toeplitz.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

Comments

patchwork-bot+netdevbpf@kernel.org Jan. 19, 2023, 5:30 p.m. UTC | #1 
Hello:

This patch was applied to netdev/net.git (master)
by Jakub Kicinski <kuba@kernel.org>:

On Wed, 18 Jan 2023 10:18:47 -0500 you wrote:
> From: Willem de Bruijn <willemb@google.com>
> 
> Avoid race between process wakeup and tpacket_v3 block timeout.
> 
> The test waits for cfg_timeout_msec for packets to arrive. Packets
> arrive in tpacket_v3 rings, which pass packets ("frames") to the
> process in batches ("blocks"). The sk waits for req3.tp_retire_blk_tov
> msec to release a block.
> 
> [...]

Here is the summary with links:
  - [net,v2] selftests/net: toeplitz: fix race on tpacket_v3 block close
    https://git.kernel.org/netdev/net/c/903848249a78

You are awesome, thank you!
diff mbox series

Patch

diff --git a/tools/testing/selftests/net/toeplitz.c b/tools/testing/selftests/net/toeplitz.c
index 90026a27eac0c..9ba03164d73a6 100644
--- a/tools/testing/selftests/net/toeplitz.c
+++ b/tools/testing/selftests/net/toeplitz.c
@@ -215,7 +215,7 @@  static char *recv_frame(const struct ring_state *ring, char *frame)
 }
 
 /* A single TPACKET_V3 block can hold multiple frames */
-static void recv_block(struct ring_state *ring)
+static bool recv_block(struct ring_state *ring)
 {
 	struct tpacket_block_desc *block;
 	char *frame;
@@ -223,7 +223,7 @@  static void recv_block(struct ring_state *ring)
 
 	block = (void *)(ring->mmap + ring->idx * ring_block_sz);
 	if (!(block->hdr.bh1.block_status & TP_STATUS_USER))
-		return;
+		return false;
 
 	frame = (char *)block;
 	frame += block->hdr.bh1.offset_to_first_pkt;
@@ -235,6 +235,8 @@  static void recv_block(struct ring_state *ring)
 
 	block->hdr.bh1.block_status = TP_STATUS_KERNEL;
 	ring->idx = (ring->idx + 1) % ring_block_nr;
+
+	return true;
 }
 
 /* simple test: sleep once unconditionally and then process all rings */
@@ -245,7 +247,7 @@  static void process_rings(void)
 	usleep(1000 * cfg_timeout_msec);
 
 	for (i = 0; i < num_cpus; i++)
-		recv_block(&rings[i]);
+		do {} while (recv_block(&rings[i]));
 
 	fprintf(stderr, "count: pass=%u nohash=%u fail=%u\n",
 		frames_received - frames_nohash - frames_error,
@@ -257,12 +259,12 @@  static char *setup_ring(int fd)
 	struct tpacket_req3 req3 = {0};
 	void *ring;
 
-	req3.tp_retire_blk_tov = cfg_timeout_msec;
+	req3.tp_retire_blk_tov = cfg_timeout_msec / 8;
 	req3.tp_feature_req_word = TP_FT_REQ_FILL_RXHASH;
 
 	req3.tp_frame_size = 2048;
 	req3.tp_frame_nr = 1 << 10;
-	req3.tp_block_nr = 2;
+	req3.tp_block_nr = 16;
 
 	req3.tp_block_size = req3.tp_frame_size * req3.tp_frame_nr;
 	req3.tp_block_size /= req3.tp_block_nr;