On 7/15/20 10:08 PM, Saravana Kannan wrote:
> Marek and Guenter reported that commit 287905e68dd2 ("driver core:
> Expose device link details in sysfs") caused sleeping/scheduling while
> atomic warnings.
>
> BUG: sleeping function called from invalid context at
> kernel/locking/mutex.c:935
> in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 12, name: kworker/0:1
> 2 locks held by kworker/0:1/12:
> #0: ee8074a8 ((wq_completion)rcu_gp){+.+.}-{0:0}, at:
> process_one_work+0x174/0x7dc
> #1: ee921f20 ((work_completion)(&sdp->work)){+.+.}-{0:0}, at:
> process_one_work+0x174/0x7dc
> Preemption disabled at:
> [<c01b10f0>] srcu_invoke_callbacks+0xc0/0x154
> ----- 8< ----- SNIP
> [<c064590c>] (device_del) from [<c0645c9c>] (device_unregister+0x24/0x64)
> [<c0645c9c>] (device_unregister) from [<c01b10fc>]
> (srcu_invoke_callbacks+0xcc/0x154)
> [<c01b10fc>] (srcu_invoke_callbacks) from [<c01493c4>]
> (process_one_work+0x234/0x7dc)
> [<c01493c4>] (process_one_work) from [<c01499b0>] (worker_thread+0x44/0x51c)
> [<c01499b0>] (worker_thread) from [<c0150bf4>] (kthread+0x158/0x1a0)
> [<c0150bf4>] (kthread) from [<c0100114>] (ret_from_fork+0x14/0x20)
> Exception stack(0xee921fb0 to 0xee921ff8)
>
> This was caused by the device link device being released in the context
> of srcu_invoke_callbacks(). There is no need to wait till the RCU
> callback to release the device link device. So release the device
> earlier and revert the RCU callback code to what it was before
> commit 287905e68dd2 ("driver core: Expose device link details in sysfs")
>
> Fixes: 287905e68dd2 ("driver core: Expose device link details in sysfs")
> Reported-by: Marek Szyprowski <m.szyprow...@samsung.com>
> Reported-by: Guenter Roeck <li...@roeck-us.net>
> Signed-off-by: Saravana Kannan <sarava...@google.com>
> ---
> Marek and Guenter,
>
> It haven't had a chance to test this yet. Can one of you please test it
> and confirm it fixes the issue?
>
With this patch applied, the original warning is gone, but I get lots
of other warnings.
WARNING: CPU: 0 PID: 1 at drivers/base/core.c:1790 device_release+0x94/0xa4^M
Device 'regulators:regulator@0:50038000.ethernet' does not have a release()
function, it is broken and must be fixed.
WARNING: CPU: 0 PID: 1 at drivers/base/core.c:1790 device_release+0x94/0xa4
Device '53f9c000.gpio:50038000.ethernet' does not have a release() function, it
is broken and must be fixed.
WARNING: CPU: 0 PID: 1 at drivers/base/core.c:1790 device_release+0x94/0xa4^M
Device '50030000.tscadc:50030400.tcq' does not have a release() function, it is
broken and must be fixed.
and so on. I don't know if this is caused by this patch or by
some other patch in -next.
Guenter
> Thanks,
> Saravana
>
> drivers/base/core.c | 10 +++-------
> 1 file changed, 3 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index 5373ddd029f6..ccb2ce11f5b5 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -306,16 +306,10 @@ static struct attribute *devlink_attrs[] = {
> };
> ATTRIBUTE_GROUPS(devlink);
>
> -static void devlink_dev_release(struct device *dev)
> -{
> - kfree(to_devlink(dev));
> -}
> -
> static struct class devlink_class = {
> .name = "devlink",
> .owner = THIS_MODULE,
> .dev_groups = devlink_groups,
> - .dev_release = devlink_dev_release,
> };
>
> static int devlink_add_symlinks(struct device *dev,
> @@ -737,7 +731,7 @@ static void device_link_free(struct device_link *link)
>
> put_device(link->consumer);
> put_device(link->supplier);
> - device_unregister(&link->link_dev);
> + kfree(link);
> }
>
> #ifdef CONFIG_SRCU
> @@ -756,6 +750,7 @@ static void __device_link_del(struct kref *kref)
> if (link->flags & DL_FLAG_PM_RUNTIME)
> pm_runtime_drop_link(link->consumer);
>
> + device_unregister(&link->link_dev);
> list_del_rcu(&link->s_node);
> list_del_rcu(&link->c_node);
> call_srcu(&device_links_srcu, &link->rcu_head, __device_link_free_srcu);
> @@ -771,6 +766,7 @@ static void __device_link_del(struct kref *kref)
> if (link->flags & DL_FLAG_PM_RUNTIME)
> pm_runtime_drop_link(link->consumer);
>
> + device_unregister(&link->link_dev);
> list_del(&link->s_node);
> list_del(&link->c_node);
> device_link_free(link);
>
