Hi Vladimir,
On Wed, Jul 4, 2018 at 10:13 AM Vladimir Zapolskiy
<vladimir_zapolskiy@xxxxxxxxxx> wrote:
> For ages trivial changes to RAVB and SuperH ethernet links by means of
> standard 'ethtool' trigger a 'sleeping function called from invalid
> context' bug, to visualize it on r8a7795 ULCB:
>
> % ethtool -r eth0
> BUG: sleeping function called from invalid context at kernel/locking/mutex.c:747
> in_atomic(): 1, irqs_disabled(): 128, pid: 554, name: ethtool
> INFO: lockdep is turned off.
> irq event stamp: 0
> hardirqs last enabled at (0): [<0000000000000000>] (null)
> hardirqs last disabled at (0): [<ffff0000080e1d3c>] copy_process.isra.7.part.8+0x2cc/0x1918
> softirqs last enabled at (0): [<ffff0000080e1d3c>] copy_process.isra.7.part.8+0x2cc/0x1918
> softirqs last disabled at (0): [<0000000000000000>] (null)
> CPU: 5 PID: 554 Comm: ethtool Not tainted 4.17.0-rc4-arm64-renesas+ #33
> Hardware name: Renesas H3ULCB board based on r8a7795 ES2.0+ (DT)
> Call trace:
> dump_backtrace+0x0/0x198
> show_stack+0x24/0x30
> dump_stack+0xb8/0xf4
> ___might_sleep+0x1c8/0x1f8
> __might_sleep+0x58/0x90
> __mutex_lock+0x50/0x890
> mutex_lock_nested+0x3c/0x50
> phy_start_aneg_priv+0x38/0x180
> phy_start_aneg+0x24/0x30
> ravb_nway_reset+0x3c/0x68
> dev_ethtool+0x3dc/0x2338
> dev_ioctl+0x19c/0x490
> sock_do_ioctl+0xe0/0x238
> sock_ioctl+0x254/0x460
> do_vfs_ioctl+0xb0/0x918
> ksys_ioctl+0x50/0x80
> sys_ioctl+0x34/0x48
> __sys_trace_return+0x0/0x4
>
> The root cause is that an attempt to modify ECMR and GECMR registers
> only when RX/TX function is disabled was too overcomplicated in its
> original implementation, also processing of an optional Link Change
> interrupt added even more complexity, as a result the implementation
> was error prone.
>
> The new locking scheme is confirmed to be correct by dumping driver
> specific and generic PHY framework function calls with aid of ftrace
> while running more or less advanced tests.
>
> Please note that sh_eth patches from the series were built-tested only.
>
> On purpose I do not add Fixes tags, the reused PHY handlers were added
> way later than the fixed problems were firstly found in the drivers.
>
> Changes from v1 to v2:
> * the original patches are split to bugfixes and enhancements only,
> both v1 and v2 series are absolutely equal in total, thus I omit
> description of changes in individual patches,
> * the latter implies that there should be no strict need for retesting,
> but because formally two series are different, I have to drop the tags
> given by Geert and Andrew, please send your tags again.
Thank for your series!
I've retested this on both R-Car M2-W (sh_eth) and R-Car H3 ES2.0 (ravb),
and the BUG disappeared.
Tested-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
