From: "Toke Høiland-Jørgensen" <toke@kernel.org>
To: Hou Tao <houtao@huaweicloud.com>, bpf@vger.kernel.org
Cc: Martin KaFai Lau <martin.lau@linux.dev>,
Alexei Starovoitov <alexei.starovoitov@gmail.com>,
Andrii Nakryiko <andrii@kernel.org>,
Eduard Zingerman <eddyz87@gmail.com>, Song Liu <song@kernel.org>,
Hao Luo <haoluo@google.com>,
Yonghong Song <yonghong.song@linux.dev>,
Daniel Borkmann <daniel@iogearbox.net>,
KP Singh <kpsingh@kernel.org>,
Stanislav Fomichev <sdf@fomichev.me>,
Jiri Olsa <jolsa@kernel.org>,
John Fastabend <john.fastabend@gmail.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
houtao1@huawei.com, xukuohai@huawei.com
Subject: Re: [PATCH bpf-next v3 1/5] bpf: Free special fields after unlock in htab_lru_map_delete_node()
Date: Fri, 17 Jan 2025 13:31:46 +0100 [thread overview]
Message-ID: <87r051oc3x.fsf@toke.dk> (raw)
In-Reply-To: <20250117101816.2101857-2-houtao@huaweicloud.com>
Hou Tao <houtao@huaweicloud.com> writes:
> From: Hou Tao <houtao1@huawei.com>
>
> When bpf_timer is used in LRU hash map, calling check_and_free_fields()
> in htab_lru_map_delete_node() will invoke bpf_timer_cancel_and_free() to
> free the bpf_timer. If the timer is running on other CPUs,
> hrtimer_cancel() will invoke hrtimer_cancel_wait_running() to spin on
> current CPU to wait for the completion of the hrtimer callback.
>
> Considering that the deletion has already acquired a raw-spin-lock
> (bucket lock). To reduce the time holding the bucket lock, move the
> invocation of check_and_free_fields() out of bucket lock. However,
> because htab_lru_map_delete_node() is invoked with LRU raw spin lock
> being held, the freeing of special fields still happens in a locked
> scope.
>
> Signed-off-by: Hou Tao <houtao1@huawei.com>
Reviewed-by: Toke Høiland-Jørgensen <toke@kernel.org>
next prev parent reply other threads:[~2025-01-17 12:31 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-01-17 10:18 [PATCH bpf-next v3 0/5] Free htab element out of bucket lock Hou Tao
2025-01-17 10:18 ` [PATCH bpf-next v3 1/5] bpf: Free special fields after unlock in htab_lru_map_delete_node() Hou Tao
2025-01-17 12:31 ` Toke Høiland-Jørgensen [this message]
2025-01-17 10:18 ` [PATCH bpf-next v3 2/5] bpf: Bail out early in __htab_map_lookup_and_delete_elem() Hou Tao
2025-01-17 12:31 ` Toke Høiland-Jørgensen
2025-01-17 10:18 ` [PATCH bpf-next v3 3/5] bpf: Free element after unlock " Hou Tao
2025-01-17 12:35 ` Toke Høiland-Jørgensen
2025-01-20 8:49 ` Hou Tao
2025-01-20 8:52 ` Toke Høiland-Jørgensen
2025-01-21 1:15 ` Hou Tao
2025-01-21 11:04 ` Toke Høiland-Jørgensen
2025-01-17 10:18 ` [PATCH bpf-next v3 4/5] bpf: Cancel the running bpf_timer through kworker for PREEMPT_RT Hou Tao
2025-01-17 12:40 ` Toke Høiland-Jørgensen
2025-01-17 10:18 ` [PATCH bpf-next v3 5/5] selftests/bpf: Add test case for the freeing of bpf_timer Hou Tao
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