| Message ID | 20210615145455.564037-10-toke@redhat.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | BPF |
| Headers | show |
| Series | Clean up and document RCU-based object protection for XDP_REDIRECT | expand |
| Context | Check | Description |
|---|---|---|
| netdev/cover_letter | success | Link |
| netdev/fixes_present | success | Link |
| netdev/patch_count | fail | Series longer than 15 patches |
| netdev/tree_selection | success | Clearly marked for bpf-next |
| netdev/subject_prefix | success | Link |
| netdev/cc_maintainers | warning | 9 maintainers not CCed: yhs@fb.com kpsingh@kernel.org daniel@iogearbox.net andrii@kernel.org hawk@kernel.org ast@kernel.org john.fastabend@gmail.com songliubraving@fb.com davem@davemloft.net |
| netdev/source_inline | success | Was 0 now: 0 |
| netdev/verify_signedoff | success | Link |
| netdev/module_param | success | Was 0 now: 0 |
| netdev/build_32bit | success | Errors and warnings before: 7 this patch: 7 |
| netdev/kdoc | success | Errors and warnings before: 0 this patch: 0 |
| netdev/verify_fixes | success | Link |
| netdev/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 50 lines checked |
| netdev/build_allmodconfig_warn | success | Errors and warnings before: 7 this patch: 7 |
| netdev/header_inline | success | Link |
diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c index 7d5cd9bc6c99..c2e9cbebc8d1 100644 --- a/drivers/net/ethernet/marvell/mvneta.c +++ b/drivers/net/ethernet/marvell/mvneta.c @@ -2370,7 +2370,6 @@ static int mvneta_rx_swbm(struct napi_struct *napi, /* Get number of received packets */ rx_todo = mvneta_rxq_busy_desc_num_get(pp, rxq); - rcu_read_lock(); xdp_prog = READ_ONCE(pp->xdp_prog); /* Fairness NAPI loop */ @@ -2421,6 +2420,10 @@ static int mvneta_rx_swbm(struct napi_struct *napi, goto next; } + /* This code is invoked within a single NAPI poll cycle and thus + * under local_bh_disable(), which provides the needed RCU + * protection. + */ if (xdp_prog && mvneta_run_xdp(pp, rxq, xdp_prog, &xdp_buf, frame_sz, &ps)) goto next; @@ -2448,7 +2451,6 @@ static int mvneta_rx_swbm(struct napi_struct *napi, xdp_buf.data_hard_start = NULL; sinfo.nr_frags = 0; } - rcu_read_unlock(); if (xdp_buf.data_hard_start) mvneta_xdp_put_buff(pp, rxq, &xdp_buf, &sinfo, -1); diff --git a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c index b2259bf1d299..658db1720826 100644 --- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c +++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c @@ -3852,8 +3852,6 @@ static int mvpp2_rx(struct mvpp2_port *port, struct napi_struct *napi, int rx_done = 0; u32 xdp_ret = 0; - rcu_read_lock(); - xdp_prog = READ_ONCE(port->xdp_prog); /* Get number of received packets and clamp the to-do */ @@ -3925,6 +3923,10 @@ static int mvpp2_rx(struct mvpp2_port *port, struct napi_struct *napi, MVPP2_MH_SIZE + MVPP2_SKB_HEADROOM, rx_bytes, false); + /* This code is invoked within a single NAPI poll cycle + * and thus under local_bh_disable(), which provides the + * needed RCU protection. + */ ret = mvpp2_run_xdp(port, xdp_prog, &xdp, pp, &ps); if (ret) { @@ -3988,8 +3990,6 @@ static int mvpp2_rx(struct mvpp2_port *port, struct napi_struct *napi, mvpp2_bm_pool_put(port, pool, dma_addr, phys_addr); } - rcu_read_unlock(); - if (xdp_ret & MVPP2_XDP_REDIR) xdp_do_flush_map();
The mvneta and mvpp2 drivers have rcu_read_lock()/rcu_read_unlock() pairs around XDP program invocations. However, the actual lifetime of the objects referred by the XDP program invocation is longer, all the way through to the call to xdp_do_flush(), making the scope of the rcu_read_lock() too small. This turns out to be harmless because it all happens in a single NAPI poll cycle (and thus under local_bh_disable()), but it makes the rcu_read_lock() misleading. Rather than extend the scope of the rcu_read_lock(), just get rid of it entirely. With the addition of RCU annotations to the XDP_REDIRECT map types that take bh execution into account, lockdep even understands this to be safe, so there's really no reason to keep it around. Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com> Cc: Marcin Wojtas <mw@semihalf.com> Cc: Russell King <linux@armlinux.org.uk> Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com> --- drivers/net/ethernet/marvell/mvneta.c | 6 ++++-- drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c | 8 ++++---- 2 files changed, 8 insertions(+), 6 deletions(-)