Messages in this thread | | | From | "Rafael J. Wysocki" <> | Date | Fri, 22 Jul 2022 19:18:42 +0200 | Subject | Re: [PATCH V2 1/1] thermal/sysfs: Clear cooling_device_stats_attr_group before initialized |
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On Fri, Jul 22, 2022 at 10:44 AM Di Shen <di.shen@unisoc.com> wrote: > > There's a space allocated for cooling_device_stats_attr_group > within cooling_device_attr_groups. This space is shared by all > cooling devices.
That's correct.
> If the stats structure of one cooling device successfully > creates stats sysfs. After that, another cooling device fails > to get max_states in cooling_device_stats_setup(). It can > return directly without initializing the stats structure, but > the cooling_device_stats_attr_group is still the attribute > group of the last cooling device.
I cannot parse the above, sorry.
For example, how can a "stats structure of one cooling device" create anything? As a data structure, it is a passive entity, so it doesn't carry out any actions.
I think (but I am not sure) that you are referring to the error code path in which the ->get_max_state() callback fails for a cooling device after cooling_device_stats_setup() has completed successfully for another one.
> At this time, read or write stats sysfs nodes can cause kernel > crash. Like the following, kernel crashed when > 'cat time_in_state_ms'. > > [<5baac8d4>] panic+0x1b4/0x3c8 > [<9d287b0f>] arm_notify_die+0x0/0x78 > [<094fc22c>] __do_kernel_fault+0x94/0xa4 > [<3b4b69a4>] do_page_fault+0xd4/0x364 > [<23793e7a>] do_translation_fault+0x38/0xc0 > [<6e5cc52a>] do_DataAbort+0x4c/0xd0 > [<a28c16b8>] __dabt_svc+0x5c/0xa0 > [<747516ae>] _raw_spin_lock+0x20/0x60 > [<9a9e4cd4>] time_in_state_ms_show+0x28/0x148 > [<cb78325e>] dev_attr_show+0x38/0x64 > [<aea3e364>] sysfs_kf_seq_show+0x8c/0xf0 > [<c0a843ab>] seq_read+0x244/0x620 > [<b316b374>] vfs_read+0xd8/0x218 > [<3aebf5fa>] sys_read+0x80/0xe4 > [<7cf100f5>] ret_fast_syscall+0x0/0x28 > [<08cbe22f>] 0xbe8c1198 > > stats sysfs: > phone:/sys/class/thermal/cooling_device2/stats # ls > reset time_in_state_ms total_trans trans_table > > The same as cat total_trans, trans_table, and echo reset. > > To avoid kernel crash, this patch set clears the > cooling_device_attr_groups before stats structure is initialized. > > Signed-off-by: Di Shen <di.shen@unisoc.com> > --- > drivers/thermal/thermal_sysfs.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/thermal/thermal_sysfs.c b/drivers/thermal/thermal_sysfs.c > index 1c4aac8464a7..e3fae63fa0f7 100644 > --- a/drivers/thermal/thermal_sysfs.c > +++ b/drivers/thermal/thermal_sysfs.c > @@ -817,6 +817,9 @@ static void cooling_device_stats_setup(struct thermal_cooling_device *cdev) > unsigned long states; > int var; > > + var = ARRAY_SIZE(cooling_device_attr_groups) - 2; > + cooling_device_attr_groups[var] = NULL; > + > if (cdev->ops->get_max_state(cdev, &states)) > return; > > --
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