During a ram_session->free call in 'core' the lock in core_env.h is taken.
Then in the ram_session::_free_ds implementation the dissolve function for the
dataspace is called. base-nova tries to make sure that the ds is not
accessible anymore by any kind of parallel incoming IPC by performing a
cleanup IPC. Unfortunately the dataspace_session implementation uses the very
same allocator in 'core' and may require to obtain the same lock as taken in
ram_session->free. This leads to a spurious deadlock on base-nova.
The actual free_ds implementation is mostly thread safe, since all used objects
inside there are already locked. The only missing piece is the _payload
variable. By changing the _payload variable in a atomic fashion there is no
need to lock the whole ram_session->free call which avoids deadlocks on
base-nova.
Fixes#549
Add functionality to lookup an object and lock it. Additional the case is
handled that a object may be already in-destruction and the lookup will deny
returning the object.
The object_pool generalize the lookup and lock functionality of the rpc_server
and serve as base for following up patches to fix dangling pointer issues.
This patch reflects eventual allocation errors in a more specific way to
the caller of 'alloc_aligned', in particular out-of-metadata and
out-of-memory are considered as different conditions.
Related to issue #526.
This patch extends the RAM session interface with the ability to
allocate DMA buffers. The client specifies the type of RAM dataspace to
allocate via the new 'cached' argument of the 'Ram_session::alloc()'
function. By default, 'cached' is true, which correponds to the common
case and the original behavior. When setting 'cached' to 'false', core
takes the precautions needed to register the memory as uncached in the
page table of each process that has the dataspace attached.
Currently, the support for allocating DMA buffers is implemented for
Fiasco.OC only. On x86 platforms, it is generally not needed. But on
platforms with more relaxed cache coherence (such as ARM), user-level
device drivers should always use uncacheable memory for DMA transactions.
