lkml.org 
[lkml]   [2013]   [Dec]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: Re: [PATCH 16/17] uprobes: Allocate ->utask before handler_chain() for tracing handlers
(2013/12/12 3:11), Oleg Nesterov wrote:
> On 12/11, Masami Hiramatsu wrote:
>>
>> (2013/12/11 0:57), Oleg Nesterov wrote:
>>> On 12/10, Masami Hiramatsu wrote:
>>>>
>>>> and isn't it better to increment
>>>> miss-hit counter of the uprobe?
>>>
>>> What do you mean? This is not miss-hit and ->utask == NULL is quite normal.
>>
>> But it could skip the handler_chain silently. It could confuse users
>> why their probe doesn't hit as expected.
>
> No, we will restart the same (probed) instruction, handle_swbp()
> will be called again, get_utask() will be called again.

Hmm, in that case, how would you avoid infinite recursive loop??
Would you repeat it until get_utask() != NULL?

> Not to mention that (in practice) if GFP_KERNEL fails the task is
> already killed.
>
>>> For example, on ppc it can be always NULL because ppc likely emulates the
>>> probed insn.
>>
>> Hmm, in that case, should uprobes handlers never be called on ppc with
>> this change?
>
> Why? With this change ppc will have ->utask != NULL even if it doesn't
> need it at all.

Ah, I see. This changes that.

Thank you,

--
Masami HIRAMATSU
IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com




\
 
 \ /
  Last update: 2013-12-12 07:41    [W:0.489 / U:0.184 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site