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Inject delay? #2336

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adam900710 opened this issue May 2, 2019 · 2 comments
Open

Inject delay? #2336

adam900710 opened this issue May 2, 2019 · 2 comments

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@adam900710
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adam900710 commented May 2, 2019 •
edited

To my understanding, injecting delay into kernel kprobe point is not supported yet due to 2 factors:

  • No way to sleep in BPF context

  • Injecting delay needs kernel developer to define where injection is possible

Unlike regular kprobe where we can only do RO operations, injecting delay, especially sleepable delay can easily screw up locking schema, e.g. injecting context switch into function with spinlock hold.

So my question is:
Is bcc/bpf going to support such injection in their road map?

With that, it should be super useful to debug race related bug.

Thanks.
@yonghong-song
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No, as far as I know, bpf community has not discussed this yet. This probably needs to be similar to injection such that a developer buy-in is needed. Also not sure how this could be implemented as sleep/block is not allowed in bpf program context. So this has to be happen outside the preempt_disable region. So this is probably not a bpf issue.

@Anjali05
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Anjali05 commented May 4, 2023

Has this been implemented yet?

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@adam900710 @Anjali05 @yonghong-song