Re: rme9652: possible deadlock

[Abramo Bagnara <abramo.bagnara@libero.it>]

Jaroslav Kysela ha scritto:
>>CPU1:
>>
>>read_lock(link_manager);	read_lock(link_manager);
>>spin_lock(s1);			spin_lock(s2);
>>if (stream_in_group)		if (stream_in_group)
>>	spin_lock(group);		spin_lock(group); /* Waiting */
>>spin_lock(s2); /* BOOM! */
>>
>>I guess that 3rd version will be the one I propose ;-)
> 
> 
> Yep, it is in CVS now ;-) Except I don't use trylock...
> 
> read_lock(link_manager);
> spin_lock(stream);
> ....
> if (stream_in_group) {
>     spin_lock(group);
>     spin_unlock(stream);
> }
> ....
> link_for_each(s) {	/* note that streams are locked in defined order now */
>     if (stream_in_group)
>         spin_lock(s);
> }
> ....
> list_for_each(s) {
>     if (stream_in_group)
>         spin_unlock(s);
> }
> ....
> if (stream_in_group) {
>     spin_lock(stream);
>     spin_unlock(group);
> }
> ....
> spin_unlock(stream);
> read_unlock(link_manager);

CPU1:				CPU2:
read_lock(link_manager);	read_lock(link_manager);
spin_lock(s1);			spin_lock(s2);
spin_lock(group);		spin_lock(group); // waiting
spin_unlock(s1);
//inside list_for_each
spin_lock(s1);
spin_lock(s2); // BOOM!

I fear you cannot avoid trylock ;-)

-- 
Abramo Bagnara                       mailto:abramo.bagnara@libero.it

Opera Unica                          Phone: +39.546.656023
Via Emilia Interna, 140
48014 Castel Bolognese (RA) - Italy



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