From: "Luis R. Rodriguez" <[email protected]> Tetsuo bisected and found that commit 786235ee "kthread: make kthread_create() killable" modified kthread_create() to bail as soon as SIGKILL is received. This is causing some issues with some drivers and at times boot. Joseph then found that failures occur as the systemd-udevd process sends SIGKILL to modprobe if probe on a driver takes over 30 seconds. When this happens probe will fail on any driver, its why booting on some system will fail if the driver happens to be a storage related driver. Some folks have suggested fixing this by modifying kthread_create() to not leave upon SIGKILL [3], upon review Oleg rejected this change and the discussion was punted out to systemd to see if the default timeout could be increased from 30 seconds to 120. The opinion of the systemd maintainers is that the driver's behavior should be fixed [4]. Linus seems to agree [5], however more recently even networking drivers have been reported to fail on probe since just writing the firmware to a device and kicking it can take easy over 60 seconds [6]. Benjamim was able to trace the issues recently reported on cxgb4 down to the same systemd-udevd 30 second timeout [6].
This is an alternative solution which enables drivers that are known to take long to use kthread_run(), this avoids the 30 second timeout and lets us annotate drivers with long init sequences that need some love. [0] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1276705 [1] https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1297248 [2] http://lists.freedesktop.org/archives/systemd-devel/2014-March/018006.html [3] http://thread.gmane.org/gmane.linux.ubuntu.devel.kernel.general/39123 [4] http://article.gmane.org/gmane.comp.sysutils.systemd.devel/17860 [5] http://article.gmane.org/gmane.linux.kernel/1671333 [6] https://bugzilla.novell.com/show_bug.cgi?id=877622 Cc: Greg Kroah-Hartman <[email protected]> Cc: Tetsuo Handa <[email protected]> Cc: Joseph Salisbury <[email protected]> Cc: Kay Sievers <[email protected]> Cc: One Thousand Gnomes <[email protected]> Cc: Tim Gardner <[email protected]> Cc: Pierre Fersing <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Oleg Nesterov <[email protected]> Cc: Benjamin Poirier <[email protected]> Cc: Greg Kroah-Hartman <[email protected]> Cc: Nagalakshmi Nandigama <[email protected]> Cc: Praveen Krishnamoorthy <[email protected]> Cc: Sreekanth Reddy <[email protected]> Cc: Abhijit Mahajan <[email protected]> Cc: Hariprasad S <[email protected]> Cc: Santosh Rastapur <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Signed-off-by: Luis R. Rodriguez <[email protected]> --- A few implementation notes: 1) Two wrappers are used to simply enable the same prototype as expected on modules for module_init() 2) The new helpers are stuffed under kthread.h since including kthread.h on init.h caused major issues which are not easy to resolve, in fact even including kernel.h in init.h cases some issues. We could have keep this under init.h if we ifef'd on _LINUX_KTHREAD_H as well but this seems a bit cleaner. include/linux/kthread.h | 35 +++++++++++++++++++++++++++++++++++ 1 file changed, 35 insertions(+) diff --git a/include/linux/kthread.h b/include/linux/kthread.h index 13d5520..2b5555a 100644 --- a/include/linux/kthread.h +++ b/include/linux/kthread.h @@ -1,6 +1,7 @@ #ifndef _LINUX_KTHREAD_H #define _LINUX_KTHREAD_H /* Simple interface for creating and stopping kernel threads without mess. */ +#include <linux/init.h> #include <linux/err.h> #include <linux/sched.h> @@ -128,4 +129,38 @@ bool queue_kthread_work(struct kthread_worker *worker, void flush_kthread_work(struct kthread_work *work); void flush_kthread_worker(struct kthread_worker *worker); +#ifndef MODULE + +#define module_long_probe_init(x) __initcall(x); +#define module_long_probe_exit(x) __exitcall(x); + +#else +/* To be used by modules which can take over 30 seconds at probe */ +#define module_long_probe_init(initfn) \ + static struct task_struct *__init_thread; \ + static int _long_probe_##initfn(void *arg) \ + { \ + return initfn(); \ + } \ + static inline __init int __long_probe_##initfn(void) \ + { \ + __init_thread = kthread_run(_long_probe_##initfn,\ + NULL, \ + #initfn); \ + if (IS_ERR(__init_thread)) \ + return PTR_ERR(__init_thread); \ + return 0; \ + } \ + module_init(__long_probe_##initfn); +/* To be used by modules that require module_long_probe_init() */ +#define module_long_probe_exit(exitfn) \ + static inline void __long_probe_##exitfn(void) \ + { \ + exitfn(); \ + if (__init_thread) \ + kthread_stop(__init_thread); \ + } \ + module_exit(__long_probe_##exitfn); +#endif /* MODULE */ + #endif /* _LINUX_KTHREAD_H */ -- 2.0.3 -- 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/
