diff mbox series

[v2,net-next,11/14] net_sched: sch_hfsc: implement lockless accesses to q->defcls

Message ID 20240418073248.2952954-12-edumazet@google.com (mailing list archive)
State Accepted
Commit 49e8ae53700212fbb26302df219922752e81fbd2
Delegated to: Netdev Maintainers
Headers show
Series net_sched: first series for RTNL-less qdisc dumps | 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: 926 this patch: 926
netdev/build_tools success No tools touched, skip
netdev/cc_maintainers success CCed 7 of 7 maintainers
netdev/build_clang success Errors and warnings before: 937 this patch: 937
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: 937 this patch: 937
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 27 lines checked
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
netdev/contest success net-next-2024-04-19--00-00 (tests: 961)

Commit Message

Eric Dumazet April 18, 2024, 7:32 a.m. UTC 
Instead of relying on RTNL, hfsc_dump_qdisc() can use READ_ONCE()
annotation, paired with WRITE_ONCE() one in hfsc_change_qdisc().

Use READ_ONCE(q->defcls) in hfsc_classify() to
no longer acquire qdisc lock from hfsc_change_qdisc().

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/sched/sch_hfsc.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

Comments

Simon Horman April 18, 2024, 3:04 p.m. UTC | #1 
On Thu, Apr 18, 2024 at 07:32:45AM +0000, Eric Dumazet wrote:
> Instead of relying on RTNL, hfsc_dump_qdisc() can use READ_ONCE()
> annotation, paired with WRITE_ONCE() one in hfsc_change_qdisc().
> 
> Use READ_ONCE(q->defcls) in hfsc_classify() to
> no longer acquire qdisc lock from hfsc_change_qdisc().
> 
> Signed-off-by: Eric Dumazet <edumazet@google.com>

Reviewed-by: Simon Horman <horms@kernel.org>
diff mbox series

Patch

diff --git a/net/sched/sch_hfsc.c b/net/sched/sch_hfsc.c
index 4e626df742d7a937c219ae9755816f099b6f0680..c287bf8423b47b7ca022fc2e6ca19b77f3ec13a0 100644
--- a/net/sched/sch_hfsc.c
+++ b/net/sched/sch_hfsc.c
@@ -1174,7 +1174,8 @@  hfsc_classify(struct sk_buff *skb, struct Qdisc *sch, int *qerr)
 	}
 
 	/* classification failed, try default class */
-	cl = hfsc_find_class(TC_H_MAKE(TC_H_MAJ(sch->handle), q->defcls), sch);
+	cl = hfsc_find_class(TC_H_MAKE(TC_H_MAJ(sch->handle),
+				       READ_ONCE(q->defcls)), sch);
 	if (cl == NULL || cl->level > 0)
 		return NULL;
 
@@ -1443,9 +1444,7 @@  hfsc_change_qdisc(struct Qdisc *sch, struct nlattr *opt,
 		return -EINVAL;
 	qopt = nla_data(opt);
 
-	sch_tree_lock(sch);
-	q->defcls = qopt->defcls;
-	sch_tree_unlock(sch);
+	WRITE_ONCE(q->defcls, qopt->defcls);
 
 	return 0;
 }
@@ -1525,7 +1524,7 @@  hfsc_dump_qdisc(struct Qdisc *sch, struct sk_buff *skb)
 	unsigned char *b = skb_tail_pointer(skb);
 	struct tc_hfsc_qopt qopt;
 
-	qopt.defcls = q->defcls;
+	qopt.defcls = READ_ONCE(q->defcls);
 	if (nla_put(skb, TCA_OPTIONS, sizeof(qopt), &qopt))
 		goto nla_put_failure;
 	return skb->len;