On Mon, 2014-04-21 at 18:38 -0400, Tejun Heo wrote: > Hello, > > On Mon, Apr 21, 2014 at 05:20:59PM +0800, Li Zhong wrote: > > While auditing the usage of lock_device_hotplug_sysfs() for implementing > > it in another way in following patch, it seems to me that the code here > > is to add/remove device, and the files probe/release for cpu bus > > themselves won't be removed. > > > > So it seems to me there is no s_active related deadlock here, and we > > could just use lock_device_hotplug(). > > It may still cause issue if offlining ends up removing sysfs files or > gets involved with the same lock used during cpu hot[un]plug > operations (e.g. offlining racing against cpu hotunplug) and offlining > a cpu does remove files. Has this change been tested?
The probe/release files are attribute files for cpu subsys, looks like following in sysfs dirs $ cd /sys/devices/system/cpu/ $ ls -l total 0 drwxr-xr-x. 7 root root 0 Apr 17 19:00 cpu0 drwxr-xr-x. 4 root root 0 Apr 17 19:00 cpu1 drwxr-xr-x. 4 root root 0 Apr 17 19:00 cpu10 ...... drwxr-xr-x. 3 root root 0 Apr 20 08:00 cpufreq drwxr-xr-x. 2 root root 0 Apr 20 08:00 cpuidle -rw-------. 1 root root 65536 Apr 21 00:28 dscr_default -r--r--r--. 1 root root 65536 Apr 21 00:28 kernel_max -r--r--r--. 1 root root 65536 Apr 21 00:28 offline -r--r--r--. 1 root root 65536 Sep 4 2014 online -r--r--r--. 1 root root 65536 Apr 21 00:28 possible drwxr-xr-x. 2 root root 0 Apr 20 08:00 power -r--r--r--. 1 root root 65536 Apr 17 20:46 present --w-------. 1 root root 65536 Apr 21 00:28 probe <----- --w-------. 1 root root 65536 Apr 21 00:28 release <----- -rw-------. 1 root root 65536 Apr 21 00:28 subcores_per_core -rw-r--r--. 1 root root 65536 Apr 21 00:28 uevent >From the code, it seems cpu subsys won't be unregistered, and it doesn't make sense to remove all the cpus in the system. Thanks, Zhong > > Thanks. > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
