From: Martin KaFai Lau <martin.lau@linux.dev>
To: bpf@vger.kernel.org
Cc: 'Alexei Starovoitov ' <ast@kernel.org>,
'Andrii Nakryiko ' <andrii@kernel.org>,
'Daniel Borkmann ' <daniel@iogearbox.net>,
'Song Liu ' <songliubraving@meta.com>,
kernel-team@meta.com
Subject: [PATCH bpf-next 6/9] bpf: bpf_task_storage_delete_recur does lookup first before the deadlock check
Date: Tue, 25 Oct 2022 11:45:21 -0700 [thread overview]
Message-ID: <20221025184524.3526117-7-martin.lau@linux.dev> (raw)
In-Reply-To: <20221025184524.3526117-1-martin.lau@linux.dev>
From: Martin KaFai Lau <martin.lau@kernel.org>
Similar to the earlier change in bpf_task_storage_get_recur.
This patch changes bpf_task_storage_delete_recur such that it
does the lookup first. It only returns -EBUSY if it needs to
take the spinlock to do the deletion when potential deadlock
is detected.
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
---
kernel/bpf/bpf_task_storage.c | 18 +++++++++++-------
1 file changed, 11 insertions(+), 7 deletions(-)
diff --git a/kernel/bpf/bpf_task_storage.c b/kernel/bpf/bpf_task_storage.c
index c3a841be438f..f3f79b618a68 100644
--- a/kernel/bpf/bpf_task_storage.c
+++ b/kernel/bpf/bpf_task_storage.c
@@ -184,7 +184,8 @@ static int bpf_pid_task_storage_update_elem(struct bpf_map *map, void *key,
return err;
}
-static int task_storage_delete(struct task_struct *task, struct bpf_map *map)
+static int task_storage_delete(struct task_struct *task, struct bpf_map *map,
+ bool nobusy)
{
struct bpf_local_storage_data *sdata;
@@ -192,6 +193,9 @@ static int task_storage_delete(struct task_struct *task, struct bpf_map *map)
if (!sdata)
return -ENOENT;
+ if (!nobusy)
+ return -EBUSY;
+
bpf_selem_unlink(SELEM(sdata), true);
return 0;
@@ -220,7 +224,7 @@ static int bpf_pid_task_storage_delete_elem(struct bpf_map *map, void *key)
}
bpf_task_storage_lock();
- err = task_storage_delete(task, map);
+ err = task_storage_delete(task, map, true);
bpf_task_storage_unlock();
out:
put_pid(pid);
@@ -289,21 +293,21 @@ BPF_CALL_5(bpf_task_storage_get, struct bpf_map *, map, struct task_struct *,
BPF_CALL_2(bpf_task_storage_delete_recur, struct bpf_map *, map, struct task_struct *,
task)
{
+ bool nobusy;
int ret;
WARN_ON_ONCE(!bpf_rcu_lock_held());
if (!task)
return -EINVAL;
- if (!bpf_task_storage_trylock())
- return -EBUSY;
-
+ nobusy = bpf_task_storage_trylock();
/* This helper must only be called from places where the lifetime of the task
* is guaranteed. Either by being refcounted or by being protected
* by an RCU read-side critical section.
*/
- ret = task_storage_delete(task, map);
- bpf_task_storage_unlock();
+ ret = task_storage_delete(task, map, nobusy);
+ if (nobusy)
+ bpf_task_storage_unlock();
return ret;
}
--
2.30.2
next prev parent reply other threads:[~2022-10-25 18:46 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-25 18:45 [PATCH bpf-next 0/9] bpf: Avoid unnecessary deadlock detection and failure in task storage Martin KaFai Lau
2022-10-25 18:45 ` [PATCH bpf-next 1/9] bpf: Remove prog->active check for bpf_lsm and bpf_iter Martin KaFai Lau
2022-10-25 18:45 ` [PATCH bpf-next 2/9] bpf: Append _recur naming to the bpf_task_storage helper proto Martin KaFai Lau
2022-10-25 18:45 ` [PATCH bpf-next 3/9] bpf: Refactor the core bpf_task_storage_get logic into a new function Martin KaFai Lau
2022-10-25 18:45 ` [PATCH bpf-next 4/9] bpf: Avoid taking spinlock in bpf_task_storage_get if potential deadlock is detected Martin KaFai Lau
2022-10-25 18:45 ` [PATCH bpf-next 5/9] bpf: Add new bpf_task_storage_get proto with no deadlock detection Martin KaFai Lau
2022-10-25 18:45 ` Martin KaFai Lau [this message]
2022-10-25 18:45 ` [PATCH bpf-next 7/9] bpf: Add new bpf_task_storage_delete " Martin KaFai Lau
2022-10-25 18:45 ` [PATCH bpf-next 8/9] selftests/bpf: Ensure no task storage failure for bpf_lsm.s prog due to " Martin KaFai Lau
2022-10-25 18:45 ` [PATCH bpf-next 9/9] selftests/bpf: Tracing prog can still do lookup under busy lock Martin KaFai Lau
2022-10-26 6:20 ` [PATCH bpf-next 0/9] bpf: Avoid unnecessary deadlock detection and failure in task storage patchwork-bot+netdevbpf
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