diff options
| author | Mark Johnston <markj@FreeBSD.org> | 2023-01-23 19:41:05 +0000 |
|---|---|---|
| committer | Mark Johnston <markj@FreeBSD.org> | 2023-02-01 17:22:31 +0000 |
| commit | b547900689ec6b500fefbf76585e7e4650a49dc2 (patch) | |
| tree | 90ee0d4e7c822b56aa33757cde200051a1d34ce2 | |
| parent | 57fa543941b82410736df2ad4a0331981ac74c67 (diff) | |
netmap: Tell the compiler to avoid reloading ring indices
Per the removed comments these fields should be loaded only once, since
they can in principle be modified concurrently, though this would be a
violation of the userspace contract with netmap.
No functional change intended.
Reviewed by: vmaffione
MFC after: 1 week
Sponsored by: Zenarmor
Sponsored by: OPNsense
Sponsored by: Klara, Inc.
Differential Revision: https://reviews.freebsd.org/D38061
(cherry picked from commit 56c438fcd4a755f0abe8254779c39a0c4b530c75)
| -rw-r--r-- | sys/dev/netmap/netmap.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/sys/dev/netmap/netmap.c b/sys/dev/netmap/netmap.c index 1b8a4ff1d5d4..8c4481c2e6c3 100644 --- a/sys/dev/netmap/netmap.c +++ b/sys/dev/netmap/netmap.c @@ -1671,8 +1671,8 @@ netmap_unget_na(struct netmap_adapter *na, struct ifnet *ifp) u_int nm_txsync_prologue(struct netmap_kring *kring, struct netmap_ring *ring) { - u_int head = ring->head; /* read only once */ - u_int cur = ring->cur; /* read only once */ + u_int head = NM_ACCESS_ONCE(ring->head); + u_int cur = NM_ACCESS_ONCE(ring->cur); u_int n = kring->nkr_num_slots; nm_prdis(5, "%s kcur %d ktail %d head %d cur %d tail %d", @@ -1749,8 +1749,8 @@ nm_rxsync_prologue(struct netmap_kring *kring, struct netmap_ring *ring) * - cur could in principle go back, however it does not matter * because we are processing a brand new rxsync() */ - cur = kring->rcur = ring->cur; /* read only once */ - head = kring->rhead = ring->head; /* read only once */ + cur = kring->rcur = NM_ACCESS_ONCE(ring->cur); + head = kring->rhead = NM_ACCESS_ONCE(ring->head); #if 1 /* kernel sanity checks */ NM_FAIL_ON(kring->nr_hwcur >= n || kring->nr_hwtail >= n); #endif /* kernel sanity checks */ |