* observe & control thread state for exit futex ?
@ 2003-04-14 2:52 John Reiser
2003-04-14 3:35 ` Daniel Jacobowitz
0 siblings, 1 reply; 3+ messages in thread
From: John Reiser @ 2003-04-14 2:52 UTC (permalink / raw)
To: linux-kernel
How can a debugger, newly attached to an arbitrary thread, determine whether
the thread has a pending exit futex and associated memory location to clear
[CLONE_CHILD_CLEARTID flag and child_tid_ptr parameter at __clone()]?
If so, then how can the debugger determine the address, change the address,
cancel the futex, and/or intercept the notification?
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: observe & control thread state for exit futex ?
2003-04-14 2:52 observe & control thread state for exit futex ? John Reiser
@ 2003-04-14 3:35 ` Daniel Jacobowitz
2003-04-15 15:01 ` John Reiser
0 siblings, 1 reply; 3+ messages in thread
From: Daniel Jacobowitz @ 2003-04-14 3:35 UTC (permalink / raw)
To: John Reiser; +Cc: linux-kernel
On Sun, Apr 13, 2003 at 07:52:08PM -0700, John Reiser wrote:
> How can a debugger, newly attached to an arbitrary thread, determine whether
> the thread has a pending exit futex and associated memory location to clear
> [CLONE_CHILD_CLEARTID flag and child_tid_ptr parameter at __clone()]?
>
> If so, then how can the debugger determine the address, change the address,
> cancel the futex, and/or intercept the notification?
It can't. Even clone flags are not accessible.
If you can think of a good reason that a debugger would need any
particular piece of data, exposing it is very straightforward.
--
Daniel Jacobowitz
MontaVista Software Debian GNU/Linux Developer
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: observe & control thread state for exit futex ?
2003-04-14 3:35 ` Daniel Jacobowitz
@ 2003-04-15 15:01 ` John Reiser
0 siblings, 0 replies; 3+ messages in thread
From: John Reiser @ 2003-04-15 15:01 UTC (permalink / raw)
To: Daniel Jacobowitz; +Cc: linux-kernel
Daniel Jacobowitz wrote:
> On Sun, Apr 13, 2003 at 07:52:08PM -0700, John Reiser wrote:
>
>>How can a debugger, newly attached to an arbitrary thread, determine whether
>>the thread has a pending exit futex and associated memory location to clear
>>[CLONE_CHILD_CLEARTID flag and child_tid_ptr parameter at __clone()]?
>>
>>If so, then how can the debugger determine the address, change the address,
>>cancel the futex, and/or intercept the notification?
>
>
> It can't. Even clone flags are not accessible.
>
> If you can think of a good reason that a debugger would need any
> particular piece of data, exposing it is very straightforward.
>
The debugger needs this information to determine the state of the thread.
An automated software audit program needs the information to verify
that threads are working correctly. In general, write-only state
[from the viewpoint of the thread] is a bad idea.
Would a new option to sys_prctl() be a good way to expose the data?
^ permalink raw reply [flat|nested] 3+ messages in thread
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