Today the get_hw_stats() API looks like this:
get_hw_stats(struct ib_device *ibdev, struct rdma_hw_stats *stats,
u8 port, int index)
The driver gets a rdma_hw_stats structure, a port and an index and is given the
possibility to:
1) Fill only the counter at location index
2) Fill all the counters
Filling the counters is done like so:
stats->value[i], 0 <= i < stats->num_counters
The stats structure is shared between all the counters. Today all the drivers
that implement get_hw_stats() always fill all the counters regardless of the
index given.
This may lead to the following scenario if we have multiple concurrent reads
of counters, cpu 0 (tries to read counter at index 0) cpu 1 (tries to read
counter at index 1)
CPU 0 CPU 1
driver: stats->value[0] = x; | ....
.... | ....
.... | ....
ib_core: return stats->value[0] to user | driver: stats->value[0] = y;
We end up with read/write to the same location at the same time.
Which can lead to providing an incorrect value to the user. This RFC introduces
a lock to protect against that.
Mark Bloch (1):
IB/core: Protect against concurrent access to hardware stats
drivers/infiniband/core/sysfs.c | 10 ++++++++--
include/rdma/ib_verbs.h | 1 +
2 files changed, 9 insertions(+), 2 deletions(-)
--
1.8.4.3
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