Messages in this thread |  | | | Date | Thu, 16 Feb 2006 15:58:23 +0100 | | From | Johannes Stezenbach <> | | Subject | Re: [patch 0/5] lightweight robust futexes: -V1 |
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On Wed, Feb 15, 2006, Ingo Molnar wrote: > "Robustness" is about dealing with crashes while holding a lock: if a > process exits prematurely while holding a pthread_mutex_t lock that is > also shared with some other process (e.g. yum segfaults while holding a > pthread_mutex_t, or yum is kill -9-ed), then waiters for that lock need > to be notified that the last owner of the lock exited in some irregular > way. ... > At the heart of this new approach there is a per-thread private list of > robust locks that userspace is holding (maintained by glibc) - which > userspace list is registered with the kernel via a new syscall [this > registration happens at most once per thread lifetime]. At do_exit() > time, the kernel checks this user-space list: are there any robust futex > locks to be cleaned up? ... > i've tested the new syscalls on x86 and x86_64, and have made sure the > parsing of the userspace list is robust [ ;-) ] even if the list is > deliberately corrupted.
I've no knowledge about all this, and maybe I didn't get your description, so forgive me if I'm talking garbage.
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?
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