From: Stephen Hemminger <stephen@networkplumber.org>
To: Marat Khalili <qm2k21@gmail.com>
Cc: Konstantin Ananyev <konstantin.ananyev@huawei.com>, dev@dpdk.org
Subject: Re: [PATCH 6/9] bpf: simplify callback inuse tracking to boolean flag
Date: Sun, 11 Oct 2026 12:51:38 -0700 [thread overview]
Message-ID: <20261011125138.75606f1c@phoenix.local> (raw)
In-Reply-To: <20261011182158.124246-7-qm2k21@gmail.com>
On Sun, 11 Oct 2026 18:21:54 +0000
Marat Khalili <qm2k21@gmail.com> wrote:
> --- a/lib/bpf/bpf_pkt.c
> +++ b/lib/bpf/bpf_pkt.c
> @@ -36,12 +36,12 @@
> * 2. Member `cb` of struct `bpf_eth_cbi`;
> * 3. Member `use` of struct `bpf_eth_cbi`;
> *
> - * BPF program is only executed if the first two are set, and increments `use` at the start and
> - * end of the callback execution so that in the safe state its value is even.
> + * BPF program is only executed if the first two are set, and sets `use` to 1 at the start and
> + * to 0 at the end of the callback execution.
> * This relies on only one thread calling the per-port/queue callback at a time.
> *
> * Unload processing starts with clearing the first two entities,
> - * then waits for `use` to become even before destroying the BPF program.
> + * then waits for `use` to become 0 before destroying the BPF program.
> * The whole operation is protected by a control-plane-only spinlock (not shown on the diagram).
> *
> * Typical sequence of synchronization actions between CP and DP on unload is shown below:
> @@ -52,7 +52,7 @@
> * | | | | | |
> * | |<---------------------- fetch callback -----------------------|
> * | | | | | |
> - * | | |<------------- increment to odd --------------|
> + * | | |<------------- store 1 -----------------------|
> * | | | | | |
> * |-- remove callback -->| | | | rte_smp_mb()
> * | | | | | |
> @@ -62,17 +62,17 @@
> * | | | | | |
> * rte_smp_mb() | | | | |
> * | | | | | |
> - * +-if use is odd | | | | if cb not NULL-+
> + * +-while use is 1 | | | | if cb not NULL-+
> * | | | | | | | |
> - * | +------------ fetch odd ------------>| | |<-- execute --+ |
> + * | +------------ fetch 1 -------------->| | |<-- execute --+ |
> * | | | | | | BPF program | |
> - * | +-while use is same | | | | +-+
> - * | | | | | | | |
> - * | | +---------- fetch odd ------------>| | | rte_smp_rmb()
> - * | | | | | | | |
> - * +-+-+ | |<------------- increment to even -------------|
> + * | | | | | | +-+
> + * | | | | | | |
> + * | | | | | | rte_smp_rmb()
> + * | | | | | | |
> + * +-+ | |<------------- store 0 -----------------------|
> * | | | | | |
> - * |------------- fetch even ------------>| | | |
> + * |------------- fetch 0 --------------->| | | |
> * | | | | | |
> * |----------------- destroy BPF program and cleanup ----------------->| |
> * | | | | | |
> @@ -87,7 +87,7 @@
> */
> struct __rte_cache_aligned bpf_eth_cbi {
> /* used by both data & control path */
> - RTE_ATOMIC(uint32_t) use; /*usage counter */
> + RTE_ATOMIC(uint32_t) use; /* usage flag: 1 when in use, 0 otherwise */
If it is only on/off now make it a bool.
next prev parent reply other threads:[~2026-10-11 19:51 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-11 18:21 [PATCH 0/9] bpf: clean up and document ethdev callback synchronization Marat Khalili
2026-10-11 18:21 ` [PATCH 1/9] bpf: document packet callback unload sequence Marat Khalili
2026-10-11 18:21 ` [PATCH 2/9] bpf: document ethdev callback threading limitations Marat Khalili
2026-10-11 18:21 ` [PATCH 3/9] bpf: reject Tx callback installation with MT_LOCKFREE Marat Khalili
2026-10-11 18:21 ` [PATCH 4/9] bpf: add callback flag to skip multi-thread check Marat Khalili
2026-10-11 19:48 ` Stephen Hemminger
2026-10-11 20:12 ` Marat Khalili
2026-10-11 18:21 ` [PATCH 5/9] bpf: remove redundant memory barrier on unload Marat Khalili
2026-10-11 19:50 ` Stephen Hemminger
2026-10-11 20:14 ` Marat Khalili
2026-10-11 18:21 ` [PATCH 6/9] bpf: simplify callback inuse tracking to boolean flag Marat Khalili
2026-10-11 19:51 ` Stephen Hemminger [this message]
2026-10-11 20:17 ` Marat Khalili
2026-10-11 18:21 ` [PATCH 7/9] bpf: reformat packet callback unload diagram Marat Khalili
2026-10-11 18:21 ` [PATCH 8/9] bpf: use relaxed stores for callback inuse tracking Marat Khalili
2026-10-11 19:52 ` Stephen Hemminger
2026-10-11 20:24 ` Marat Khalili
2026-10-11 18:21 ` [PATCH 9/9] bpf: make callback handle atomic with relaxed access Marat Khalili
2026-10-11 19:54 ` Stephen Hemminger
2026-10-11 20:31 ` Marat Khalili
2026-10-11 20:29 ` [RFC] bpf: fix callback unload with concurrent Tx burst Stephen Hemminger
2026-10-12 21:09 ` [PATCH v2 0/9] bpf: clean up and document ethdev callback synchronization Marat Khalili
2026-10-12 21:09 ` [PATCH v2 1/9] bpf: document packet callback unload sequence Marat Khalili
2026-10-12 21:09 ` [PATCH v2 2/9] bpf: document ethdev callback threading limitations Marat Khalili
2026-10-12 21:44 ` Stephen Hemminger
2026-10-12 21:09 ` [PATCH v2 3/9] bpf: reject Tx callback installation with MT_LOCKFREE Marat Khalili
2026-10-12 21:09 ` [PATCH v2 4/9] bpf: remove redundant memory barrier on unload Marat Khalili
2026-10-12 21:09 ` [PATCH v2 5/9] bpf: simplify callback inuse tracking to boolean flag Marat Khalili
2026-10-12 21:09 ` [PATCH v2 6/9] bpf: reformat packet callback unload diagram Marat Khalili
2026-10-12 21:09 ` [PATCH v2 7/9] bpf: use relaxed accesses for callback inuse tracking Marat Khalili
2026-10-12 21:09 ` [PATCH v2 8/9] bpf: make callback handle atomic with relaxed access Marat Khalili
2026-10-12 21:09 ` [PATCH v2 9/9] bpf: add callback flag to skip multi-thread check Marat Khalili
2026-10-13 16:55 ` Stephen Hemminger
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