Re: L4Re: region mapper/manager concurrency considerations and resource limits

Hi,

On Sunday, 07.02.2021, 01:54 +0100 Paul Boddie wrote:
> What considerations need to be given to concurrency with regard to
> the use of 
> the l4re_rm_attach function and similar functionality? Is access to
> the region 
> mapper/manager from different threads in the same task advisable, are
> there 
> thread safety issues, and if so, can these be sensibly worked around?

Calls to the region manager are IPC calls and are synchronized by a
wait-queue in the kernel. The region manager thread only serves one
client at a time. In fact if you use multiple threads in a task it
serves all page-faults for all threads already. It's thread-safe by
design.

However, the capability slot allocator (l4re_util_cap_alloc) is not
thread-safe. You need to introduce some synchronization if you use it
from multiple threads.

Hope that helps.


 - Christian