diff mbox series

[net-next,2/3] net: rps: protect filter locklessly

Message ID 20240416074232.23525-3-kerneljasonxing@gmail.com (mailing list archive)
State Superseded
Delegated to: Netdev Maintainers
Headers show
Series locklessly protect left members in struct rps_dev_flow | expand

Checks

Context Check Description
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for net-next
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 935 this patch: 935
netdev/build_tools success No tools touched, skip
netdev/cc_maintainers success CCed 4 of 4 maintainers
netdev/build_clang fail Errors and warnings before: 16 this patch: 16
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 947 this patch: 947
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 18 lines checked
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 79 this patch: 79
netdev/source_inline success Was 0 now: 0

Commit Message

Jason Xing April 16, 2024, 7:42 a.m. UTC 
From: Jason Xing <kernelxing@tencent.com>

As we can see, rflow->filter can be written/read concurrently, so
lockless access is needed.

Signed-off-by: Jason Xing <kernelxing@tencent.com>
---
I'm not very sure if the READ_ONCE in set_rps_cpu() is useful. I
scaned/checked the codes and found no lock can prevent multiple
threads from calling set_rps_cpu() and handling the same flow
simultaneously. The same question still exists in patch [3/3].
---
 net/core/dev.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)
diff mbox series

Patch

diff --git a/net/core/dev.c b/net/core/dev.c
index cd97eeae8218..6892682f9cbf 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4524,8 +4524,8 @@  set_rps_cpu(struct net_device *dev, struct sk_buff *skb,
 			goto out;
 		old_rflow = rflow;
 		rflow = &flow_table->flows[flow_id];
-		rflow->filter = rc;
-		if (old_rflow->filter == rflow->filter)
+		WRITE_ONCE(rflow->filter, rc);
+		if (old_rflow->filter == READ_ONCE(rflow->filter))
 			old_rflow->filter = RPS_NO_FILTER;
 	out:
 #endif
@@ -4666,7 +4666,7 @@  bool rps_may_expire_flow(struct net_device *dev, u16 rxq_index,
 	if (flow_table && flow_id <= flow_table->mask) {
 		rflow = &flow_table->flows[flow_id];
 		cpu = READ_ONCE(rflow->cpu);
-		if (rflow->filter == filter_id && cpu < nr_cpu_ids &&
+		if (READ_ONCE(rflow->filter) == filter_id && cpu < nr_cpu_ids &&
 		    ((int)(READ_ONCE(per_cpu(softnet_data, cpu).input_queue_head) -
 			   READ_ONCE(rflow->last_qtail)) <
 		     (int)(10 * flow_table->mask)))