Abstract the complexity of iterating over all the fences
in a dma_resv object.
The new loop handles the whole RCU and retry dance and
returns only fences where we can be sure we grabbed the
right one.
v2: fix accessing the shared fences while they might be freed,
improve kerneldoc, rename _cursor to _iter, add
dma_resv_iter_is_exclusive, add dma_resv_iter_begin/end
v3: restructor the code, move rcu_read_lock()/unlock() into the
iterator, add dma_resv_iter_is_restarted()
v4: fix NULL deref when no explicit fence exists, drop superflous
rcu_read_lock()/unlock() calls.
v5: fix typos in the documentation
v6: fix coding error when excl fence is NULL
v7: one more logic fix
v8: fix index check in dma_resv_iter_is_exclusive()
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> (v7)
Link: https://patchwork.freedesktop.org/patch/msgid/20211005113742.1101-2-christian.koenig@amd.com
c921ff373b