Re: [patch 0/5] lightweight robust futexes: -V1

From: Daniel Walker
Date: Thu Feb 16 2006 - 14:03:08 EST


On Thu, 16 Feb 2006, Ingo Molnar wrote:


* Johannes Stezenbach <js@xxxxxxxxxxx> wrote:

Anyway: If a process can trash its robust futext list and then die
with a segfault, why are the futexes still robust? In this case the
kernel has no way to wake up waiters with FUTEX_OWNER_DEAD, or does
it?

that's memory corruption - which robust futexes do not (and cannot)
solve. Robustness is mostly about handling sudden death (e.g. which is
due to oom, or is due to a user killing the task, or due to the
application crashing in some non-memory-corrupting way), but it cannot
handle all possible failure modes.

I don't think this is a weakness in Dave or Inaky's versions. Dave at least maintained the bulk of the information in kernel space. The uaddr was used for the fast locking in userspace, but not for maintaining the robustness .

Correct me if I'm wrong Dave.

Daniel
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/