lkml.org 
[lkml]   [2018]   [Jul]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v5 06/10] Uprobes: Support SDT markers having reference count (semaphore)
On 06/28, Ravi Bangoria wrote:
>
> @@ -294,6 +462,15 @@ int uprobe_write_opcode(struct uprobe *uprobe, struct mm_struct *mm,
> if (ret <= 0)
> goto put_old;
>
> + /* Update the ref_ctr if we are going to replace instruction. */
> + if (!ref_ctr_updated) {
> + ret = update_ref_ctr(uprobe, mm, is_register);
> + if (ret)
> + goto put_old;
> +
> + ref_ctr_updated = 1;
> + }

Why can't this code live in install_breakpoint() and remove_breakpoint() ?
this way we do not need to export "struct uprobe" and change set_swbp/set_orig_insn,
and the logic will be more simple.

And let me ask again... May be you have already explained this, but I can't
find the previous discussion.

So why do we need a counter but not a boolean? IIRC, because the counter can
be shared, in particular 2 different uprobes can have the same >ref_ctr_offset,
right?

But who else can use this counter and how? Say, can userspace update it too?
If yes, why this can't race with __update_ref_ctr() ?

And btw, why does __update_ref_ctr() use FOLL_FORCE? This vma should be writeable
or valid_ref_ctr_vma() should nack it?

And shouldn't valid_ref_ctr_vma() check VM_SHARED? IIUC we do not want to write
to this file?

Oleg.

\
 
 \ /
  Last update: 2018-07-01 23:11    [W:0.168 / U:0.020 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site