Thomas Gleixner 46c498c2cd stop_machine: Mark per cpu stopper enabled early ... commit 14e568e78 (stop_machine: Use smpboot threads) introduced the following regression: Before this commit the stopper enabled bit was set in the online notifier. CPU0 CPU1 cpu_up cpu online hotplug_notifier(ONLINE) stopper(CPU1)->enabled = true; ... stop_machine() The conversion to smpboot threads moved the enablement to the wakeup path of the parked thread. The majority of users seem to have the following working order: CPU0 CPU1 cpu_up cpu online unpark_threads() wakeup(stopper[CPU1]) .... stopper thread runs stopper(CPU1)->enabled = true; stop_machine() But Konrad and Sander have observed: CPU0 CPU1 cpu_up cpu online unpark_threads() wakeup(stopper[CPU1]) .... stop_machine() stopper thread runs stopper(CPU1)->enabled = true; Now the stop machinery kicks CPU0 into the stop loop, where it gets stuck forever because the queue code saw stopper(CPU1)->enabled == false, so CPU0 waits for CPU1 to enter stomp_machine, but the CPU1 stopper work got discarded due to enabled == false. Add a pre_unpark function to the smpboot thread descriptor and call it before waking the thread. This fixes the problem at hand, but the stop_machine code should be more robust. The stopper->enabled flag smells fishy at best. Thanks to Konrad for going through a loop of debug patches and providing the information to decode this issue. Reported-and-tested-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Reported-and-tested-by: Sander Eikelenboom <linux@eikelenboom.it> Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> Cc: Rusty Russell <rusty@rustcorp.com.au> Link: http://lkml.kernel.org/r/alpine.LFD.2.02.1302261843240.22263@ionos Signed-off-by: Thomas Gleixner <tglx@linutronix.de>		2013-02-26 22:25:17 +01:00
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acpi	PCI changes for the v3.8 merge window:	2012-12-13 12:14:47 -08:00
asm-generic	This implements the cputime accounting on full dynticks CPUs.	2013-02-05 13:10:33 +01:00
clocksource
crypto
drm	Merge branch 'drm-intel-fixes' of git://people.freedesktop.org/~danvet/drm-intel	2013-01-11 07:52:48 +10:00
keys
linux	stop_machine: Mark per cpu stopper enabled early	2013-02-26 22:25:17 +01:00
math-emu
media
memory
misc
net	ipv6: rename datagram_send_ctl and datagram_recv_ctl	2013-01-31 13:53:08 -05:00
pcmcia
ras
rdma	UAPI: Remove empty Kbuild files	2013-01-02 17:36:10 -08:00
rxrpc
scsi	SCSI misc on 20121212	2012-12-13 19:20:31 -08:00
sound	Merge remote-tracking branch 'asoc/fix/cs4271' into tmp	2013-01-10 12:22:11 +00:00
target	target: Introduce TCM_NO_SENSE	2013-01-10 20:06:08 -08:00
trace	Merge branch 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2013-02-19 17:49:41 -08:00
uapi	Merge branch 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2013-02-19 17:49:41 -08:00
video	Merge branch 'omap-for-v3.8/fixes-for-merge-window' into omap-for-v3.8/fixes-for-merge-window-v2	2012-12-16 11:28:10 -08:00
xen	Bugfixes:	2012-12-18 12:26:54 -08:00
Kbuild	UAPI: Remove empty Kbuild files	2013-01-02 17:36:10 -08:00