[Date Prev][Date Next]
Re: [LMDB] Lockups with robust mutexes and crashing processes
Marcos-David Dione wrote:
Marcos-David Dione/NCE/AMADEUS wrote on 24/11/2014 11:10:42:
> Seen like that I'm not sure if there's a defined behaviour
> for that. I'll ask in the glibc and/or kernel MLs and I'll come
> back with the answer.
and here's the answer:
> On 11/24/2014 03:34 PM, Marcos Dione wrote:
> > We found a situation where a robust mutex cannot be recovered
> > from a stale lock and we're wondering if it's simply an undefined
> > situation or a bug in the kernel. Attached you will find the sample
> > code, which is loosely based on a glibc's test case.The gist of it
> > follows:
> > 1. we open a file.
> > 2. we mmap it and use that mem to store a robust mutex.
> > 3. we lock the mutex.
> > 4. we munmap the file.
> > 5. we close the file.
> Undefined behaviour.
> This results in undefined behaviour since the allocated storage for
> the mutex object has been lost. You need to keep that storage around
> for the robust algorithms to work with. Without any data you can't
> do anything.
Fyi, this would not have been a bug in Solaris:
-- Howard Chu
CTO, Symas Corp. http://www.symas.com
Director, Highland Sun http://highlandsun.com/hyc/
Chief Architect, OpenLDAP http://www.openldap.org/project/