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Subject: Re: [PATCH bpf-next v4 1/2] bpf: extend stackmap to save
 binary_build_id+offset instead of address
To: Song Liu <songliubraving@fb.com>
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From: Alexei Starovoitov <ast@fb.com>
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Date: Mon, 12 Mar 2018 14:31:46 -0700
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On 3/12/18 2:12 PM, Song Liu wrote:
>
>> On Mar 12, 2018, at 2:00 PM, Alexei Starovoitov <ast@fb.com> wrote:
>>
>> On 3/12/18 1:39 PM, Song Liu wrote:
>>> +	page = find_get_page(vma->vm_file->f_mapping, 0);
>>
>> did you test it with config_debug_atomic_sleep ?
>> it should have complained...
>
> Yeah, I have CONFIG_DEBUG_ATOMIC_SLEEP=y.
>
> I think find_get_page() will not sleep. The variation find_get_page_flags()
> may sleep with flag FGP_CREAT.

I see. gfp_mask == 0 and no locks. should work indeed.
curious how perf report looks like for heavy bpf_get_stackid() usage?