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| author | Michael S. Tsirkin <mst@dev.mellanox.co.il> | 2007-05-21 19:06:54 +0300 |
|---|---|---|
| committer | Roland Dreier <rolandd@cisco.com> | 2007-05-21 13:41:29 -0700 |
| commit | 9f81036c54ed1f860d2807c5a6aa4f2b30c21204 (patch) | |
| tree | ab0eacf7aa4a78bce8aa96073678244d01c8175d /drivers/infiniband | |
| parent | 518b1646f8a31904ca637b8df0c1e31c34a7a3c2 (diff) | |
| download | lwn-9f81036c54ed1f860d2807c5a6aa4f2b30c21204.tar.gz lwn-9f81036c54ed1f860d2807c5a6aa4f2b30c21204.zip | |
IB/cm: Improve local id allocation
The IB CM uses an idr for local id allocations, with a running counter
as start_id. This fails to generate distinct ids if
1. An id is constantly created and destroyed
2. A chunk of ids just beyond the current next_id value is occupied
This in turn leads to an increased chance of connection request being
mis-detected as a duplicate, sometimes for several retries, until
next_id gets past the block of allocated ids. This has been observed
in practice.
As a fix, remember the last id allocated and start immediately above it.
This also fixes a problem with the old code, where next_id might
overflow and become negative.
Signed-off-by: Michael S. Tsirkin <mst@dev.mellanox.co.il>
Acked-by: Sean Hefty <sean.hefty@intel.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>
Diffstat (limited to 'drivers/infiniband')
| -rw-r--r-- | drivers/infiniband/core/cm.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/drivers/infiniband/core/cm.c b/drivers/infiniband/core/cm.c index eff591deeb46..e840434a96d8 100644 --- a/drivers/infiniband/core/cm.c +++ b/drivers/infiniband/core/cm.c @@ -306,7 +306,9 @@ static int cm_alloc_id(struct cm_id_private *cm_id_priv) do { spin_lock_irqsave(&cm.lock, flags); ret = idr_get_new_above(&cm.local_id_table, cm_id_priv, - next_id++, &id); + next_id, &id); + if (!ret) + next_id = ((unsigned) id + 1) & MAX_ID_MASK; spin_unlock_irqrestore(&cm.lock, flags); } while( (ret == -EAGAIN) && idr_pre_get(&cm.local_id_table, GFP_KERNEL) ); |