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Clarify that bus_dma does not stall future load requests once a load is

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deferred.  The caller is required to enforce that if that is desired.

MFC after:	2 weeks
This commit is contained in:
John Baldwin 2012-08-30 14:44:30 +00:00
parent 3932d76033
commit 28b5187f44
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=239906
1 changed files with 7 additions and 2 deletions
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9
share/man/man9/bus_dma.9
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@ -580,8 +580,13 @@ The status of the mapping has been delivered to the callback.
The mapping has been deferred for lack of resources.
The callback will be called as soon as resources are available.
Callbacks are serviced in FIFO order.
To ensure that ordering is guaranteed, all subsequent load requests will also
be deferred until all callbacks have been processed.
.Pp
Note that subsequent load operations for the same tag that do not require
extra resources will still succeed.
This may result in out-of-order processing of requests.
If the caller requires the order of requests to be preserved,
then the caller is required to stall subsequent requests until a pending
request's callback is invoked.
.It Er ENOMEM
The load request has failed due to insufficient resources, and the caller
specifically used the