Serge E. Hallyn wrote:
> Quoting Matt Helsley (matthltc@xxxxxxxxxx):
>> diff --git a/checkpoint/process.c b/checkpoint/process.c
>> index b604a85..084a2e4 100644
>> --- a/checkpoint/process.c
>> +++ b/checkpoint/process.c
>> @@ -42,6 +42,17 @@ static int checkpoint_task_struct(struct ckpt_ctx *ctx, struct task_struct *t)
>>
>> h->task_comm_len = TASK_COMM_LEN;
>>
>> +#ifdef CONFIG_FUTEX
>> + /* These are __user pointers and can be saved without the objhash. */
>> + h->robust_futex_list = t->robust_list;
>> + h->robust_futex_head_len = sizeof(t->robust_list);
>> +#ifdef CONFIG_COMPAT
>> + h->compat_robust_futex_list = t->compat_robust_list;
>> + h->compat_robust_futex_head_len = sizeof(t->compat_robust_list);
>> +#endif
>> + /* FIXME save pi futex state?? */
>> +#endif
>> +
>
> So, I'm torn on this, but this does look like a prime example of code
> which is destined to go stale and out of sync with the main futex code.
>
> On the other hand, if we define futex_checkpoint() and futex_restart(),
> and do that for every little thing we c/r, that could get out of hand...
>
> But I think it's a risk worth taking. What do you think?
Which risk is the one worth taking ? -- I assume splitting the c/r
code to smaller pieces near/at related subsystems source code. The
question is: where do you draw the line ?
(This is also related to Andrew Morgan's concern about capabilities).
I think that for a "self-contained" object (e.g. capabilities),
it makes much sense to separate it.
I'm not so sure about passing struct ckpt_task_struct_hdr around
to small functions to fill it... can become very scattered. And
a dedicated "futex" object doesn't make sense either.
If anything, perhaps use a 'struct ckpt_task_futex' which will
be embedded in ckpt_task_struct_hdr:
struct ckpt_task_struct_hdr {
struct ckpt_hdr h;
...
struct ckpt_task_futex futex;
...
};
There are more examples, for instance:
* nsproxy: in checkpoint/process.c or in kernel/nxproxy.c ?
* uts_ns: in checkpoint/process.c or in kernel/utsname.c ?
And also:
* files/fd: in checkpoint/files.c or in fs/checkpoint.c ?
* memory: in checkpoint/memory.c or in mm/checkpoint.c ?
Originally it seemed natural to keep everything under checkpoint/
subdir. The cost is (a) risks getting out of sync, and (b) need
to export functions that could remain static/private otherwise.
Comments ?
Oren.
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