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| author | Michal Schmidt <mschmidt@redhat.com> | 2023-06-06 10:12:53 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2023-06-07 10:51:58 +0100 |
| commit | bf15bb38ec7f4ff522da5c20e1673dbda7159938 (patch) | |
| tree | e012fb729354d7f343b9f277938f4ccd7381c33c /drivers/net/ethernet/intel/ice/ice_common.c | |
| parent | d636fc5dd692c8f4e00ae6e0359c0eceeb5d9bdb (diff) | |
| download | lwn-bf15bb38ec7f4ff522da5c20e1673dbda7159938.tar.gz lwn-bf15bb38ec7f4ff522da5c20e1673dbda7159938.zip | |
ice: make writes to /dev/gnssX synchronous
The current ice driver's GNSS write implementation buffers writes and
works through them asynchronously in a kthread. That's bad because:
- The GNSS write_raw operation is supposed to be synchronous[1][2].
- There is no upper bound on the number of pending writes.
Userspace can submit writes much faster than the driver can process,
consuming unlimited amounts of kernel memory.
A patch that's currently on review[3] ("[v3,net] ice: Write all GNSS
buffers instead of first one") would add one more problem:
- The possibility of waiting for a very long time to flush the write
work when doing rmmod, softlockups.
To fix these issues, simplify the implementation: Drop the buffering,
the write_work, and make the writes synchronous.
I tested this with gpsd and ubxtool.
[1] https://events19.linuxfoundation.org/wp-content/uploads/2017/12/The-GNSS-Subsystem-Johan-Hovold-Hovold-Consulting-AB.pdf
"User interface" slide.
[2] A comment in drivers/gnss/core.c:gnss_write():
/* Ignoring O_NONBLOCK, write_raw() is synchronous. */
[3] https://patchwork.ozlabs.org/project/intel-wired-lan/patch/20230217120541.16745-1-karol.kolacinski@intel.com/
Fixes: d6b98c8d242a ("ice: add write functionality for GNSS TTY")
Signed-off-by: Michal Schmidt <mschmidt@redhat.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Tested-by: Sunitha Mekala <sunithax.d.mekala@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers/net/ethernet/intel/ice/ice_common.c')
| -rw-r--r-- | drivers/net/ethernet/intel/ice/ice_common.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/net/ethernet/intel/ice/ice_common.c b/drivers/net/ethernet/intel/ice/ice_common.c index 0157f6e98d3e..eb2dc0983776 100644 --- a/drivers/net/ethernet/intel/ice/ice_common.c +++ b/drivers/net/ethernet/intel/ice/ice_common.c @@ -5160,7 +5160,7 @@ ice_aq_read_i2c(struct ice_hw *hw, struct ice_aqc_link_topo_addr topo_addr, */ int ice_aq_write_i2c(struct ice_hw *hw, struct ice_aqc_link_topo_addr topo_addr, - u16 bus_addr, __le16 addr, u8 params, u8 *data, + u16 bus_addr, __le16 addr, u8 params, const u8 *data, struct ice_sq_cd *cd) { struct ice_aq_desc desc = { 0 }; |