On Mon, Dec 10, 2018 at 11:35 AM Alexander Duyck <alexander.h.du...@linux.intel.com> wrote: > > On Mon, 2018-12-10 at 10:58 -0800, Dan Williams wrote: > > On Wed, Dec 5, 2018 at 9:25 AM Alexander Duyck > > <alexander.h.du...@linux.intel.com> wrote: > > > > > > Add an additional bit flag to the device struct named "dead". > > > > > > This additional flag provides a guarantee that when a device_del is > > > executed on a given interface an async worker will not attempt to attach > > > the driver following the earlier device_del call. Previously this > > > guarantee was not present and could result in the device_del call > > > attempting to remove a driver from an interface only to have the async > > > worker attempt to probe the driver later when it finally completes the > > > asynchronous probe call. > > > > > > Signed-off-by: Alexander Duyck <alexander.h.du...@linux.intel.com> > > > --- > > > drivers/base/core.c | 11 +++++++++++ > > > drivers/base/dd.c | 8 ++++++-- > > > include/linux/device.h | 5 +++++ > > > 3 files changed, 22 insertions(+), 2 deletions(-) > > > > > > diff --git a/drivers/base/core.c b/drivers/base/core.c > > > index f3e6ca4170b4..70358327303b 100644 > > > --- a/drivers/base/core.c > > > +++ b/drivers/base/core.c > > > @@ -2075,6 +2075,17 @@ void device_del(struct device *dev) > > > struct kobject *glue_dir = NULL; > > > struct class_interface *class_intf; > > > > > > + /* > > > + * Hold the device lock and set the "dead" flag to guarantee that > > > + * the update behavior is consistent with the other bitfields near > > > + * it and that we cannot have an asynchronous probe routine trying > > > + * to run while we are tearing out the bus/class/sysfs from > > > + * underneath the device. > > > + */ > > > + device_lock(dev); > > > + dev->dead = true; > > > + device_unlock(dev); > > > + > > > /* Notify clients of device removal. This call must come > > > * before dpm_sysfs_remove(). > > > */ > > > diff --git a/drivers/base/dd.c b/drivers/base/dd.c > > > index 88713f182086..3bb8c3e0f3da 100644 > > > --- a/drivers/base/dd.c > > > +++ b/drivers/base/dd.c > > > @@ -774,6 +774,10 @@ static void __device_attach_async_helper(void *_dev, > > > async_cookie_t cookie) > > > > > > device_lock(dev); > > > > > > + /* device is or has been removed from the bus, just bail out */ > > > + if (dev->dead) > > > + goto out_unlock; > > > + > > > > What do you think about moving this check into > > __device_attach_driver() alongside all the other checks? That way we > > also get ->dead checking through the __device_attach() path. > > I'm not really sure that is the best spot to do that. Part of the > reason being that by placing it where I did we avoid messing with the > runtime power management for the parent if it was already powered off.
...but this already a rare event and the parent shouldn't otherwise be bothered by a spurious pm_runtime wakeup event. > If anything I would say we could probably look at pulling the check out > and placing the driver check in __device_attach_async_helper since from > what I can tell the check is actually redundant in the non-async path > anyway since __device_attach already had taken the device lock and > checked dev->driver prior to calling __device_attach_driver. > > > ...and after that maybe it could be made a common helper > > (dev_driver_checks()?) shared between __device_attach_driver() and > > __driver_attach() to reduce some duplication. > > I'm not sure consolidating it into a function would really be worth the > extra effort. It would essentially just obfuscate the checks and I am > not sure you really save much with: > if (dev_driver_checks(dev)) > vs: > if (!dev->dead && !dev->driver) > > By the time you create the function and replace the few spots that are > making these checks you would end up most likely adding more complexity > to the kernel rather than reducing it any. No, I was talking about removing this duplication in __device_attach_driver() and __driver_attach(): if (ret == 0) { /* no match */ return 0; } else if (ret == -EPROBE_DEFER) { dev_dbg(dev, "Device match requests probe deferral\n"); driver_deferred_probe_add(dev); } else if (ret < 0) { dev_dbg(dev, "Bus failed to match device: %d", ret); return ret; } /* ret > 0 means positive match */ ...and lead in with a dev->dead check. _______________________________________________ Linux-nvdimm mailing list Linux-nvdimm@lists.01.org https://lists.01.org/mailman/listinfo/linux-nvdimm