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Em Quinta-feira 27. Maio 2010, =C3=A0s 16.43.20, Lubos Lunak escreveu:
>  If this is an important issue to fix, what is the patch and the problem=
=20
> (=3Dsomething specific) it fixes?

The patch is attached to the bugzilla report that Sebastian linked to.

It can't be applied to the current 1.2 tree because it contains a behaviour=
=20
change in one of the basic event-loop integration callbacks.

The issue in question is that, when libdbus-1 needs to call the callback fo=
r=20
enabling, disabling or toggling timers, or socket notifiers (DBusTimeout an=
d=20
DBusWatch in libdbus-1 parlance), it needs to drop the locks. It's standard=
=20
procedure: you're calling out to user code, you drop all locks you have in=
=20
place, because the user may do strange things and recurse back to you.

The problem is that, if we drop the locks, then a recursion may change the=
=20
pointers in the structures that were being modified (think reallocation). S=
o=20
libdbus-1 has had for years now this hack that doesn't work that simply mak=
es=20
the pointer NULL to indicate that a recursion has happened.

Couple that with threading and you have this issue happening when two separ=
ate=20
threads try to send a D-Bus message at the same time: when one drops its=20
locks, the other one tries to send, and finds the structures set to NULL. T=
hat=20
second one fails without setting a proper error message, which in libdbus-1=
=20
means "Out of memory".

The fix is to *not* drop the locks and document what the binding may or may=
 not=20
do in that callback.

=2D-=20
Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
  Senior Product Manager - Nokia, Qt Development Frameworks
      PGP/GPG: 0x6EF45358; fingerprint:
      E067 918B B660 DBD1 105C  966C 33F5 F005 6EF4 5358

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