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authorHaggai Eran <haggaie@mellanox.com>2015-07-30 17:50:13 +0300
committerDoug Ledford <dledford@redhat.com>2015-08-30 15:48:15 -0400
commit5aa44bb90f047662c12c44be1b6de454658632d0 (patch)
treeef9f18b75a5794c055e5fa8c8fd3a38ae2d1e231 /net/rds
parent3403051ebbd486a342272a404f16e7f1aca8758e (diff)
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op-kernel-dev-5aa44bb90f047662c12c44be1b6de454658632d0.tar.gz
IB/core: Add rwsem to allow reading device list or client list
Currently the RDMA subsystem's device list and client list are protected by a single mutex. This prevents adding user-facing APIs that iterate these lists, since using them may cause a deadlock. The patch attempts to solve this problem by adding a read-write semaphore to protect the lists. Readers now don't need the mutex, and are safe just by read-locking the semaphore. The ib_register_device, ib_register_client, ib_unregister_device, and ib_unregister_client functions are modified to lock the semaphore for write during their respective list modification. Also, in order to make sure client callbacks are called only between add() and remove() calls, the code is changed to only add items to the lists after the add() calls and remove from the lists before the remove() calls. This patch attempts to solve a similar need [1] that was seen in the RoCE v2 patch series. [1] http://www.spinics.net/lists/linux-rdma/msg24733.html Reviewed-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com> Cc: Matan Barak <matanb@mellanox.com> Signed-off-by: Haggai Eran <haggaie@mellanox.com> Signed-off-by: Doug Ledford <dledford@redhat.com>
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