Messages in this thread |  | | Date | Tue, 21 Jun 2011 15:47:04 +0530 | | From | Santosh Shilimkar <> | | Subject | Re: [RFC PATCH] ARM: smp: Fix the CPU hotplug race with scheduler. |
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On 6/21/2011 3:30 PM, Russell King - ARM Linux wrote: > On Tue, Jun 21, 2011 at 02:38:34PM +0530, Santosh Shilimkar wrote: >> Russell, >> >> On 6/20/2011 8:24 PM, Santosh Shilimkar wrote: >>> On 6/20/2011 7:53 PM, Russell King - ARM Linux wrote: >>>> So, as loops_per_jiffy is not local to this function, the compiler has >>>> to write out that zero value, before calling calibrate_delay_converge(), >>>> and loops_per_jiffy only becomes non-zero _after_ >>>> calibrate_delay_converge() >>>> has returned. This opens the window and allows the spinlock debugging >>>> code to explode. >>>> >>>> This patch closes the window completely, by only writing to >>>> loops_per_jiffy >>>> only when we have a real value for it. >>>> >>>> This allows me to boot 3.0.0-rc3 on Versatile Express (4 CPU) whereas >>>> without this it fails with spinlock lockup and rcu problems. >>>> >>>> init/calibrate.c | 14 ++++++++------ >>>> 1 files changed, 8 insertions(+), 6 deletions(-) >>>> >>> I am away from my board now. Will test this change. >> Have tested your change and it seems to fix the crash I >> was observing. Are you planning to send this fix for rc5? > > Yes. I think sending CPUs into infinite loops in the spinlock code is > definitely sufficiently serious that it needs to go to Linus ASAP. > It'd be nice to have a tested-by line though. > Sure.
>>> btw, the online-active race is still open even with this patch close >>> and should be fixed. >>> >> The only problem remains is waiting for active mask before >> marking CPU online. Shall I refresh my patch with only >> this change then ? > > I already have that as a separate change. Can you point me to both of these commits so that I have them in my tree for testing.
Thanks for help.
Regards Santosh
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