| Message ID | 20230210100131.3088240-7-jiri@resnulli.us (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 280f7b2adca09c8d5f34b99f49e5c570aa81daad |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | devlink: params cleanups and devl_param_driverinit_value_get() fix | expand |
| Context | Check | Description |
|---|---|---|
| netdev/tree_selection | success | Clearly marked for net-next |
| netdev/fixes_present | success | Fixes tag not required for -next series |
| netdev/subject_prefix | success | Link |
| netdev/cover_letter | success | Series has a cover letter |
| netdev/patch_count | success | Link |
| netdev/header_inline | success | No static functions without inline keyword in header files |
| netdev/build_32bit | success | Errors and warnings before: 2 this patch: 2 |
| netdev/cc_maintainers | success | CCed 9 of 9 maintainers |
| netdev/build_clang | success | Errors and warnings before: 1 this patch: 1 |
| netdev/module_param | success | Was 0 now: 0 |
| netdev/verify_signedoff | success | Signed-off-by tag matches author and committer |
| netdev/check_selftest | success | No net selftest shell script |
| netdev/verify_fixes | success | Fixes tag looks correct |
| netdev/build_allmodconfig_warn | success | Errors and warnings before: 2 this patch: 2 |
| netdev/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 25 lines checked |
| netdev/kdoc | success | Errors and warnings before: 0 this patch: 0 |
| netdev/source_inline | success | Was 0 now: 0 |
On 2/10/2023 2:01 AM, Jiri Pirko wrote: > From: Jiri Pirko <jiri@nvidia.com> > > If the driver maintains following basic sane behavior, the > devl_param_driverinit_value_get() function could be called without > holding instance lock: > > 1) Driver ensures a call to devl_param_driverinit_value_get() cannot > race with registering/unregistering the parameter with > the same parameter ID. > 2) Driver ensures a call to devl_param_driverinit_value_get() cannot > race with devl_param_driverinit_value_set() call with > the same parameter ID. > 3) Driver ensures a call to devl_param_driverinit_value_get() cannot > race with reload operation. > > By the nature of params usage, these requirements should be > trivially achievable. If the driver for some off reason > is not able to comply, it has to take the devlink->lock while > calling devl_param_driverinit_value_get(). > > Remove the lock assertion and add comment describing > the locking requirements. > > This fixes a splat in mlx5 driver introduced by the commit > referenced in the "Fixes" tag. Just to clarify, is it possible for mlx5 to take the instance lock instead of these changes? I agree the improvements make sense here, but it seems like an alternative fix would be to grab the lock around the get function call in mlx5. Either way, the assumptions here seem reasonable and the series makes sense. Reviewed-by: Jacob Keller <jacob.e.keller@intel.com> Thanks, Jake > > Lore: https://lore.kernel.org/netdev/719de4f0-76ac-e8b9-38a9-167ae239efc7@amd.com/ > Reported-by: Kim Phillips <kim.phillips@amd.com> > Fixes: 075935f0ae0f ("devlink: protect devlink param list by instance lock") > Signed-off-by: Jiri Pirko <jiri@nvidia.com> > Reviewed-by: Simon Horman <simon.horman@corigine.com> > Acked-by: Jakub Kicinski <kuba@kernel.org> > --- > net/devlink/leftover.c | 13 +++++++++++-- > 1 file changed, 11 insertions(+), 2 deletions(-) > > diff --git a/net/devlink/leftover.c b/net/devlink/leftover.c > index 6d3988f4e843..9f0256c2c323 100644 > --- a/net/devlink/leftover.c > +++ b/net/devlink/leftover.c > @@ -9628,14 +9628,23 @@ EXPORT_SYMBOL_GPL(devlink_params_unregister); > * > * This function should be used by the driver to get driverinit > * configuration for initialization after reload command. > + * > + * Note that lockless call of this function relies on the > + * driver to maintain following basic sane behavior: > + * 1) Driver ensures a call to this function cannot race with > + * registering/unregistering the parameter with the same parameter ID. > + * 2) Driver ensures a call to this function cannot race with > + * devl_param_driverinit_value_set() call with the same parameter ID. > + * 3) Driver ensures a call to this function cannot race with > + * reload operation. > + * If the driver is not able to comply, it has to take the devlink->lock > + * while calling this. > */ > int devl_param_driverinit_value_get(struct devlink *devlink, u32 param_id, > union devlink_param_value *val) > { > struct devlink_param_item *param_item; > > - lockdep_assert_held(&devlink->lock); > - > if (WARN_ON(!devlink_reload_supported(devlink->ops))) > return -EOPNOTSUPP; >
On 2/10/23 4:01 AM, Jiri Pirko wrote: > From: Jiri Pirko <jiri@nvidia.com> > > If the driver maintains following basic sane behavior, the > devl_param_driverinit_value_get() function could be called without > holding instance lock: > > 1) Driver ensures a call to devl_param_driverinit_value_get() cannot > race with registering/unregistering the parameter with > the same parameter ID. > 2) Driver ensures a call to devl_param_driverinit_value_get() cannot > race with devl_param_driverinit_value_set() call with > the same parameter ID. > 3) Driver ensures a call to devl_param_driverinit_value_get() cannot > race with reload operation. > > By the nature of params usage, these requirements should be > trivially achievable. If the driver for some off reason > is not able to comply, it has to take the devlink->lock while > calling devl_param_driverinit_value_get(). > > Remove the lock assertion and add comment describing > the locking requirements. > > This fixes a splat in mlx5 driver introduced by the commit > referenced in the "Fixes" tag. > > Lore: https://lore.kernel.org/netdev/719de4f0-76ac-e8b9-38a9-167ae239efc7@amd.com/ > Reported-by: Kim Phillips <kim.phillips@amd.com> > Fixes: 075935f0ae0f ("devlink: protect devlink param list by instance lock") > Signed-off-by: Jiri Pirko <jiri@nvidia.com> > Reviewed-by: Simon Horman <simon.horman@corigine.com> > Acked-by: Jakub Kicinski <kuba@kernel.org> > --- Please add my: Tested-by: Kim Phillips <kim.phillips@amd.com> to this patch, if not the entire series. Thanks! Kim p.s. Sorry about my testing snafu on v1 of this series - it wasn't clear to me what fixes were where...
Fri, Feb 10, 2023 at 08:41:27PM CET, jacob.e.keller@intel.com wrote: > > >On 2/10/2023 2:01 AM, Jiri Pirko wrote: >> From: Jiri Pirko <jiri@nvidia.com> >> >> If the driver maintains following basic sane behavior, the >> devl_param_driverinit_value_get() function could be called without >> holding instance lock: >> >> 1) Driver ensures a call to devl_param_driverinit_value_get() cannot >> race with registering/unregistering the parameter with >> the same parameter ID. >> 2) Driver ensures a call to devl_param_driverinit_value_get() cannot >> race with devl_param_driverinit_value_set() call with >> the same parameter ID. >> 3) Driver ensures a call to devl_param_driverinit_value_get() cannot >> race with reload operation. >> >> By the nature of params usage, these requirements should be >> trivially achievable. If the driver for some off reason >> is not able to comply, it has to take the devlink->lock while >> calling devl_param_driverinit_value_get(). >> >> Remove the lock assertion and add comment describing >> the locking requirements. >> >> This fixes a splat in mlx5 driver introduced by the commit >> referenced in the "Fixes" tag. > >Just to clarify, is it possible for mlx5 to take the instance lock >instead of these changes? I agree the improvements make sense here, but >it seems like an alternative fix would be to grab the lock around the >get function call in mlx5. You are correct, yes. > >Either way, the assumptions here seem reasonable and the series makes sense. > >Reviewed-by: Jacob Keller <jacob.e.keller@intel.com> > >Thanks, >Jake > >> >> Lore: https://lore.kernel.org/netdev/719de4f0-76ac-e8b9-38a9-167ae239efc7@amd.com/ >> Reported-by: Kim Phillips <kim.phillips@amd.com> >> Fixes: 075935f0ae0f ("devlink: protect devlink param list by instance lock") >> Signed-off-by: Jiri Pirko <jiri@nvidia.com> >> Reviewed-by: Simon Horman <simon.horman@corigine.com> >> Acked-by: Jakub Kicinski <kuba@kernel.org> >> --- >> net/devlink/leftover.c | 13 +++++++++++-- >> 1 file changed, 11 insertions(+), 2 deletions(-) >> >> diff --git a/net/devlink/leftover.c b/net/devlink/leftover.c >> index 6d3988f4e843..9f0256c2c323 100644 >> --- a/net/devlink/leftover.c >> +++ b/net/devlink/leftover.c >> @@ -9628,14 +9628,23 @@ EXPORT_SYMBOL_GPL(devlink_params_unregister); >> * >> * This function should be used by the driver to get driverinit >> * configuration for initialization after reload command. >> + * >> + * Note that lockless call of this function relies on the >> + * driver to maintain following basic sane behavior: >> + * 1) Driver ensures a call to this function cannot race with >> + * registering/unregistering the parameter with the same parameter ID. >> + * 2) Driver ensures a call to this function cannot race with >> + * devl_param_driverinit_value_set() call with the same parameter ID. >> + * 3) Driver ensures a call to this function cannot race with >> + * reload operation. >> + * If the driver is not able to comply, it has to take the devlink->lock >> + * while calling this. >> */ >> int devl_param_driverinit_value_get(struct devlink *devlink, u32 param_id, >> union devlink_param_value *val) >> { >> struct devlink_param_item *param_item; >> >> - lockdep_assert_held(&devlink->lock); >> - >> if (WARN_ON(!devlink_reload_supported(devlink->ops))) >> return -EOPNOTSUPP; >>
diff --git a/net/devlink/leftover.c b/net/devlink/leftover.c index 6d3988f4e843..9f0256c2c323 100644 --- a/net/devlink/leftover.c +++ b/net/devlink/leftover.c @@ -9628,14 +9628,23 @@ EXPORT_SYMBOL_GPL(devlink_params_unregister); * * This function should be used by the driver to get driverinit * configuration for initialization after reload command. + * + * Note that lockless call of this function relies on the + * driver to maintain following basic sane behavior: + * 1) Driver ensures a call to this function cannot race with + * registering/unregistering the parameter with the same parameter ID. + * 2) Driver ensures a call to this function cannot race with + * devl_param_driverinit_value_set() call with the same parameter ID. + * 3) Driver ensures a call to this function cannot race with + * reload operation. + * If the driver is not able to comply, it has to take the devlink->lock + * while calling this. */ int devl_param_driverinit_value_get(struct devlink *devlink, u32 param_id, union devlink_param_value *val) { struct devlink_param_item *param_item; - lockdep_assert_held(&devlink->lock); - if (WARN_ON(!devlink_reload_supported(devlink->ops))) return -EOPNOTSUPP;