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netdevsim: psp: use atomic64 for psp stats counters

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The existing u64_stats_t-based psp counters had two preexisting api
usage bugs: u64_stats_init() was never called on the syncp object, and
the writer side of the u64_stats_update_begin()/end() api was not
serialized. Switch the counters to atomic64_t instead. Atomics need
no initialization and are inherently safe against concurrent writers,
eliminating both bugs at once.

Use atomic64_t rather than atomic_long_t so byte counters don't wrap
at 4 GiB on 32-bit builds.

Fixes: 178f0763c5 ("netdevsim: implement psp device stats")
Cc: <stable+noautosel@kernel.org> # netdevsim is a test harness, it's never loaded on production systems
Signed-off-by: Daniel Zahka <daniel.zahka@gmail.com>
Link: https://patch.msgid.link/20260529-fix-psp-stats-v2-2-3a194eacf18e@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Daniel Zahka 2026-05-29 06:15:28 -07:00 committed by Jakub Kicinski
parent abaef7e966
commit 163bea8010
2 changed files with 12 additions and 22 deletions
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10
drivers/net/netdevsim/netdevsim.h
View File

@ -22,7 +22,6 @@
#include <linux/list.h>
#include <linux/netdevice.h>
#include <linux/ptp_mock.h>
#include <linux/u64_stats_sync.h>
#include <net/devlink.h>
#include <net/udp_tunnel.h>
#include <net/xdp.h>
@ -115,11 +114,10 @@ struct netdevsim {
int rq_reset_mode;
struct {
u64_stats_t rx_packets;
u64_stats_t rx_bytes;
u64_stats_t tx_packets;
u64_stats_t tx_bytes;
struct u64_stats_sync syncp;
atomic64_t rx_packets;
atomic64_t rx_bytes;
atomic64_t tx_packets;
atomic64_t tx_bytes;
struct psp_dev __rcu *dev;
struct dentry *rereg;
struct mutex rereg_lock;

24
drivers/net/netdevsim/psp.c
View File

@ -50,10 +50,8 @@ nsim_do_psp(struct sk_buff *skb, struct netdevsim *ns,
}
psp_len = skb->len - skb_inner_transport_offset(skb);
u64_stats_update_begin(&ns->psp.syncp);
u64_stats_inc(&ns->psp.tx_packets);
u64_stats_add(&ns->psp.tx_bytes, psp_len);
u64_stats_update_end(&ns->psp.syncp);
atomic64_inc(&ns->psp.tx_packets);
atomic64_add(psp_len, &ns->psp.tx_bytes);
/* Now pretend we just received this frame */
peer_psd = rcu_dereference(peer_ns->psp.dev);
@ -79,10 +77,8 @@ nsim_do_psp(struct sk_buff *skb, struct netdevsim *ns,
refcount_inc(&(*psp_ext)->refcnt);
skb->decrypted = 1;
u64_stats_update_begin(&peer_ns->psp.syncp);
u64_stats_inc(&peer_ns->psp.rx_packets);
u64_stats_add(&peer_ns->psp.rx_bytes, psp_len);
u64_stats_update_end(&peer_ns->psp.syncp);
atomic64_inc(&peer_ns->psp.rx_packets);
atomic64_add(psp_len, &peer_ns->psp.rx_bytes);
} else {
struct ipv6hdr *ip6h __maybe_unused;
struct iphdr *iph;
@ -191,20 +187,16 @@ static void nsim_assoc_del(struct psp_dev *psd, struct psp_assoc *pas)
static void nsim_get_stats(struct psp_dev *psd, struct psp_dev_stats *stats)
{
struct netdevsim *ns = psd->drv_priv;
unsigned int start;
/* WARNING: do *not* blindly zero stats in real drivers!
* All required stats must be reported by the device!
*/
memset(stats, 0, sizeof(struct psp_dev_stats));
do {
start = u64_stats_fetch_begin(&ns->psp.syncp);
stats->rx_bytes = u64_stats_read(&ns->psp.rx_bytes);
stats->rx_packets = u64_stats_read(&ns->psp.rx_packets);
stats->tx_bytes = u64_stats_read(&ns->psp.tx_bytes);
stats->tx_packets = u64_stats_read(&ns->psp.tx_packets);
} while (u64_stats_fetch_retry(&ns->psp.syncp, start));
stats->rx_bytes = atomic64_read(&ns->psp.rx_bytes);
stats->rx_packets = atomic64_read(&ns->psp.rx_packets);
stats->tx_bytes = atomic64_read(&ns->psp.tx_bytes);
stats->tx_packets = atomic64_read(&ns->psp.tx_packets);
}
static struct psp_dev_ops nsim_psp_ops = {