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| author | Martin KaFai Lau <martin.lau@kernel.org> | 2022-10-25 11:45:21 -0700 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2022-10-25 23:11:46 -0700 |
| commit | fda64ae0bb3e37b5a4292625c6931cb156224d0f (patch) | |
| tree | 27fa66933685435b9a643e29b0fb0c9aa3b4c14a /kernel/bpf | |
| parent | 4279adb094a17132423f1271c3d11b593fc2327e (diff) | |
| download | lwn-fda64ae0bb3e37b5a4292625c6931cb156224d0f.tar.gz lwn-fda64ae0bb3e37b5a4292625c6931cb156224d0f.zip | |
bpf: bpf_task_storage_delete_recur does lookup first before the deadlock check
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>
Link: https://lore.kernel.org/r/20221025184524.3526117-7-martin.lau@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel/bpf')
| -rw-r--r-- | kernel/bpf/bpf_task_storage.c | 18 |
1 files 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 @@ out: 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; } |