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authorRoland Dreier <rolandd@cisco.com>2006-06-17 20:44:49 -0700
committerRoland Dreier <rolandd@cisco.com>2006-06-17 20:44:49 -0700
commit9ead190bfde2a434c74ea604382d08acb2eceef5 (patch)
tree937f1bb8dedea56efc46aed12370bb3865898763 /net
parentIB/mthca: Make all device methods truly reentrant (diff)
IB/uverbs: Don't serialize with ib_uverbs_idr_mutex
Currently, all userspace verbs operations that call into the kernel are serialized by ib_uverbs_idr_mutex. This can be a scalability issue for some workloads, especially for devices driven by the ipath driver, which needs to call into the kernel even for datapath operations. Fix this by adding reference counts to the userspace objects, and then converting ib_uverbs_idr_mutex into a spinlock that only protects the idrs long enough to take a reference on the object being looked up. Because remove operations may fail, we have to do a slightly funky two-step deletion, which is described in the comments at the top of uverbs_cmd.c. This also still leaves ib_uverbs_idr_lock as a single lock that is possibly subject to contention. However, the lock hold time will only be a single idr operation, so multiple threads should still be able to make progress, even if ib_uverbs_idr_lock is being ping-ponged. Surprisingly, these changes even shrink the object code: add/remove: 23/5 grow/shrink: 4/21 up/down: 633/-693 (-60) Signed-off-by: Roland Dreier <rolandd@cisco.com>
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