Hi, Jonathan Best Regards! Anson Huang > -----Original Message----- > > On Mon, 8 Apr 2019 02:07:24 +0000 > Anson Huang <anson.huang@xxxxxxx> wrote: > > > Hi, Jonathan > > > > Best Regards! > > Anson Huang > > > > > -----Original Message----- > > > From: Jonathan Cameron [mailto:jic23@xxxxxxxxxx] > > > Sent: 2019年4月7日 18:40 > > > To: Anson Huang <anson.huang@xxxxxxx> > > > Cc: knaack.h@xxxxxx; lars@xxxxxxxxxx; pmeerw@xxxxxxxxxx; > Leonard > > > Crestez <leonard.crestez@xxxxxxx>; gustavo@xxxxxxxxxxxxxx; > > > martink@xxxxxxxxx; rtresidd@xxxxxxxxxxxxxxxxx; > > > linux-iio@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > > > dl-linux-imx <linux-imx@xxxxxxx> > > > Subject: [EXT] Re: [PATCH] iio: accell: mma8452: free iio trigger > > > pointer when cleanup > > > > > > WARNING: This email was created outside of NXP. DO NOT CLICK links > > > or attachments unless you recognize the sender and know the content is > safe. > > > > > > > > > > > > On Thu, 4 Apr 2019 08:02:05 +0000 > > > Anson Huang <anson.huang@xxxxxxx> wrote: > > > > > > > When mma8452 is built as module, once it is insmod and rmmod, > > > > below kernel dump will show out, the root cause is module being > > > > put twice if iio trigger pointer is NOT NULL, this patch frees iio > > > > trigger pointer after iio trigger is unregistered to avoid below > > > > kernel > > > > dump: > > > > > > > > ------------[ cut here ]------------ > > > > WARNING: CPU: 3 PID: 270 at kernel/module.c:1145 > > > module_put+0xd0/0x188 > > > > Modules linked in: mma8452(-) > > > > CPU: 3 PID: 270 Comm: rmmod Not tainted > > > > 5.1.0-rc3-next-20190403-00022-g5ede0c9-dirty #1596 Hardware name: > > > > Freescale i.MX6 Quad/DualLite (Device Tree) [<c011272c>] > > > > (unwind_backtrace) from [<c010d094>] (show_stack+0x10/0x14) > > > > [<c010d094>] (show_stack) from [<c0bdc160>] > > > > (dump_stack+0xd8/0x10c) [<c0bdc160>] (dump_stack) from > > > > [<c01275d8>] (__warn+0xf8/0x124) [<c01275d8>] (__warn) from > > > > [<c0127714>] > > > (warn_slowpath_null+0x3c/0x48) > > > > [<c0127714>] (warn_slowpath_null) from [<c01ca4d0>] > > > > (module_put+0xd0/0x188) [<c01ca4d0>] (module_put) from > > > > [<c08a5bb4>] > > > > (iio_device_unregister_trigger_consumer+0x18/0x24) > > > > [<c08a5bb4>] (iio_device_unregister_trigger_consumer) from > > > > [<c08a0ab4>] (iio_dev_release+0x20/0) [<c08a0ab4>] > > > > (iio_dev_release) from [<c065c0e8>] (device_release+0x24/0x8c) > > > > [<c065c0e8>] > > > > (device_release) from [<c0be1810>] (kobject_put+0x74/0xd4) > > > > [<c0be1810>] (kobject_put) from [<c0664dc0>] > > > > (release_nodes+0x16c/0x1f0) [<c0664dc0>] (release_nodes) from > > > > [<c0661b80>] (device_release_driver_internal+0xec/0x1a0) > > > > [<c0661b80>] (device_release_driver_internal) from [<c0661c90>] > > > > (driver_detach+0x44/0x80) [<c0661c90>] (driver_detach) from > > > > [<c066096c>] (bus_remove_driver+0x4c/0xa0) [<c066096c>] > > > > (bus_remove_driver) from [<c01cc1a4>] > > > > (sys_delete_module+0x130/0x1dc) [<c01cc1a4>] (sys_delete_module) > > > > from [<c0101000>] > > > (ret_fast_syscall+0x0/0x28) Exception stack(0xe8d87fa8 to > > > 0xe8d87ff0) > > > > 7fa0: 0001ffc0 38616d6d be87bbf0 00000880 00000000 > be87be98 > > > > 7fc0: 0001ffc0 38616d6d 00323534 00000081 000a9744 be87bf81 > > > > 000a9790 > > > > 00000000 > > > > 7fe0: be87bbe8 be87bbd8 0001fe18 b6e381a0 irq event stamp: 4017 > > > > hardirqs last enabled at (4035): [<c0188a0c>] > > > > console_unlock+0x400/0x630 hardirqs last disabled at (4052): > > > > [<c018868c>] console_unlock+0x80/0x630 softirqs last enabled at > > > > (4050): [<c0102698>] __do_softirq+0x458/0x554 softirqs last > > > > disabled at (4069): [<c012ed6c>] irq_exit+0x130/0x180 ---[ end > > > > trace > > > > a7ba8f1823b1e073 ]--- > > > > > > > > Signed-off-by: Anson Huang <Anson.Huang@xxxxxxx> > > > Good fine, but the fix is not in the best place. The key thing is > > > that any assignment inside a driver to iio_dev->trig should be done > > > with iio_trigger_get. > > > > > > indio_dev->trig = iio_trigger_get(trig). The intent is to avoid > > > this exact double free, but also handle it correctly if we are using devm_ > for all the handling. > > > > > > I just did a grep and there are quite a few drivers not doing this > > > though so it's one we should be more careful about. > > > > > > Hmm. Anyone fancy doing an audit of existing drivers and checking > > > which ones have this problem? Some seem to do exactly what you have > > > here, but that isn't a the best pattern to encourage. > > > > > > For this one would you mind trying with the iio_trigger_get approach > > > and if I'm not missing something, send a v2 fixing it that way? > > > > With below patch to use iio_trigger_get, looks like > > try_release_module_ref() will return 1 and cause try_stop_module() > > return fail and we will see " rmmod: can't unload 'mma8452': Resource > > temporarily unavailable ", > > > > As the module ref count check is before > > iio_device_unregister_trigger_consumer() is called which will do > iio_trigger_put(), so looks like there is still something wrong with the module > ref count? > Hmm. Drivers that grab their own triggers are a bit of a pain. We need the > infrastructure to try to prevent trigger drivers going away, but it can cause > self references. > > For this particular driver the validation is only that the trigger is not used with > a different device. You can use a different trigger with this device I believe? > > As such, we shouldn't really be setting this default at all. However, removing > it now will break userspace that is assuming the default trigger is set. > (setting a trigger should always be a userspace decision, rather than hard > coded unless there is a clear one to one mapping - mind you we have this > same problem if we have a fixed trigger, though in that case we have > trig_readonly set so we can know it's happening and there is an easy fix). > > The right option, I think, is to remove the trigger manually before removing > the driver. This is admittedly a bit ugly. > > echo '' > /sys/bus/iio/devices/iio:\devicesX/current_trigger. > > rmmod mma8452 > > Can you confirm if that works as expected? After removing the current_trigger, below Oops will occur when remove the mma8452 module. Any other idea? i.mx8mm-evk# cat /sys/bus/iio/devices/iio\:device2/trigger/current_trigger mma8451-dev2 i.mx8mm-evk# echo > /sys/bus/iio/devices/iio\:device2/trigger/current_trigger i.mx8mm-evk# cat /sys/bus/iio/devices/iio\:device2/trigger/current_trigger i.mx8mm-evk# i.mx8mm-evk# i.mx8mm-evk# i.mx8mm-evk# i.mx8mm-evk# rmmod mma8452 [ 93.004967] Internal error: Oops - undefined instruction: 0 [#1] SMP ARM [ 93.011696] Modules linked in: mma8452 [ 93.015460] CPU: 1 PID: 272 Comm: rmmod Not tainted 5.1.0-rc4-next-20190415-00009-gef9b7e5-dirty #1756 [ 93.024771] Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree) [ 93.031316] PC is at sys_delete_module+0x1c0/0x1dc [ 93.036112] LR is at 0x32 [ 93.038739] pc : [<c01cc3d8>] lr : [<00000032>] psr: a0070013 [ 93.045012] sp : e8b23f58 ip : bf0041d3 fp : 00000000 [ 93.050242] r10: 00000081 r9 : e8b22000 r8 : c01011c4 [ 93.055472] r7 : 00000081 r6 : be85cbf0 r5 : c1908908 r4 : bf0041c0 [ 93.062004] r3 : bf0043fc r2 : 00000000 r1 : ffffffff r0 : 00000000 [ 93.068538] Flags: NzCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none [ 93.075677] Control: 10c5387d Table: 3875004a DAC: 00000051 [ 93.081429] Process rmmod (pid: 272, stack limit = 0x(ptrval)) [ 93.087267] Stack: (0xe8b23f58 to 0xe8b24000) [ 93.091630] 3f40: 38616d6d 00323534 [ 93.099816] 3f60: 00000001 c190eb04 00000017 b6ea74e0 e8b23fb0 10c5387d 000a9758 00000002 [ 93.108001] 3f80: be85c72c c011799c 00000001 c0101068 00cd0c80 38f6dac7 0001ffc0 38616d6d [ 93.116186] 3fa0: 00323534 c0101000 0001ffc0 38616d6d be85cbf0 00000880 00000000 be85ce98 [ 93.124370] 3fc0: 0001ffc0 38616d6d 00323534 00000081 000a9744 be85cf81 000a9790 00000000 [ 93.132555] 3fe0: be85cbe8 be85cbd8 0001fe18 b6e551a0 60070010 be85cbf0 00000000 00000000 [ 93.140746] [<c01cc3d8>] (sys_delete_module) from [<c0101000>] (ret_fast_syscall+0x0/0x28) [ 93.149014] Exception stack(0xe8b23fa8 to 0xe8b23ff0) [ 93.154073] 3fa0: 0001ffc0 38616d6d be85cbf0 00000880 00000000 be85ce98 [ 93.162258] 3fc0: 0001ffc0 38616d6d 00323534 00000081 000a9744 be85cf81 000a9790 00000000 [ 93.170440] 3fe0: be85cbe8 be85cbd8 0001fe18 b6e551a0 [ 93.175501] Code: 0affffd6 ee072fba e3e0400a eaffffb2 (e7f001f2) [ 93.181604] ---[ end trace d1b72b60c2108067 ]--- Segmentation fault Anson. > > Thanks, > > Jonathan > > > > +++ b/drivers/iio/accel/mma8452.c > > @@ -1468,17 +1468,15 @@ static int mma8452_trigger_setup(struct > iio_dev *indio_dev) > > if (ret) > > return ret; > > > > - indio_dev->trig = trig; > > + indio_dev->trig = iio_trigger_get(trig); > > > > Thanks, > > Anson. > > > > > > > > Thanks > > > > > > Jonathan > > > > > > > > > > --- > > > > drivers/iio/accel/mma8452.c | 4 +++- > > > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > > > > > diff --git a/drivers/iio/accel/mma8452.c > > > > b/drivers/iio/accel/mma8452.c index 3027811..6b18177 100644 > > > > --- a/drivers/iio/accel/mma8452.c > > > > +++ b/drivers/iio/accel/mma8452.c > > > > @@ -1475,8 +1475,10 @@ static int mma8452_trigger_setup(struct > > > > iio_dev > > > > *indio_dev) > > > > > > > > static void mma8452_trigger_cleanup(struct iio_dev *indio_dev) { > > > > - if (indio_dev->trig) > > > > + if (indio_dev->trig) { > > > > iio_trigger_unregister(indio_dev->trig); > > > > + indio_dev->trig = NULL; > > > > + } > > > > } > > > > > > > > static int mma8452_reset(struct i2c_client *client) > >
