Hi Silas, On Thu, 2 Aug 2012 17:07:08 -0700, Silas Boyd-Wickizer wrote: > via_cputemp_init in drivers/hwmon/via-cputemp.c loops with > for_each_online_cpu, adding platform_devices, then calls > register_hotcpu_notifier. If a CPU is offlined between the loop and > register_hotcpu_notifier, then later onlined, via_cputemp_device_add > will attempt to platform devices with the same ID.
Missing word in this last sentence. > > This fix surrounds for_each_online_cpu and register_hotcpu_notifier > with get_online_cpus+put_online_cpus. > > Build tested. Thanks for reporting and for the fix. Two questions: What about via_cputemp_exit()? While less obvious, I suspect it is racy too. The notifier is unregistered first. If a CPU gets offline before the devices are removed, we will have a device pointing to a non-existent CPU for a short time. I think we should play it safe and use get/put_online_cpus() there too, as I seem to understand it guarantees CPUs can't go offline when we wouldn't handle that event properly. Alternatively, unregistering the platform driver first might close the race. Secondly, drivers/hwmon/coretemp.c is very similar to via-cputemp.c, so I think it needs the exact same fix(es). > > Signed-off-by: Silas Boyd-Wickizer <[email protected]> > --- > drivers/hwmon/via-cputemp.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/hwmon/via-cputemp.c b/drivers/hwmon/via-cputemp.c > index 8689664..9ad07c3 100644 > --- a/drivers/hwmon/via-cputemp.c > +++ b/drivers/hwmon/via-cputemp.c > @@ -328,6 +328,7 @@ static int __init via_cputemp_init(void) > if (err) > goto exit; > > + get_online_cpus(); > for_each_online_cpu(i) { > struct cpuinfo_x86 *c = &cpu_data(i); > > @@ -347,12 +348,14 @@ static int __init via_cputemp_init(void) > > #ifndef CONFIG_HOTPLUG_CPU > if (list_empty(&pdev_list)) { > + put_online_cpus(); > err = -ENODEV; > goto exit_driver_unreg; > } > #endif > > register_hotcpu_notifier(&via_cputemp_cpu_notifier); > + put_online_cpus(); > return 0; > > #ifndef CONFIG_HOTPLUG_CPU -- Jean Delvare -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
