Messages in this thread | | | Date | Thu, 9 Mar 2017 07:24:59 -0800 | From | "Paul E. McKenney" <> | Subject | Re: RCU used on incoming CPU before rcu_cpu_starting() called |
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On Thu, Mar 09, 2017 at 02:08:23PM +0100, Thomas Gleixner wrote: > On Wed, 8 Mar 2017, Paul E. McKenney wrote: > > [ 30.694013] lockdep_rcu_suspicious+0xe7/0x120 > > [ 30.694013] get_work_pool+0x82/0x90 > > [ 30.694013] __queue_work+0x70/0x5f0 > > [ 30.694013] queue_work_on+0x33/0x70 > > [ 30.694013] clear_sched_clock_stable+0x33/0x40 > > [ 30.694013] early_init_intel+0xe7/0x2f0 > > [ 30.694013] init_intel+0x11/0x350 > > [ 30.694013] identify_cpu+0x344/0x5a0 > > [ 30.694013] identify_secondary_cpu+0x18/0x80 > > [ 30.694013] smp_store_cpu_info+0x39/0x40 > > [ 30.694013] start_secondary+0x4e/0x100 > > [ 30.694013] start_cpu+0x14/0x14 > > > > Here is the relevant code from x86's smp_callin(): > > > > /* > > * Save our processor parameters. Note: this information > > * is needed for clock calibration. > > */ > > smp_store_cpu_info(cpuid); > > > > The problem is that smp_store_cpu_info() indirectly invokes > > schedule_work(), which wants to use RCU. But RCU isn't informed > > of the incoming CPU until the call to notify_cpu_starting(), which > > causes lockdep to complain bitterly about the use of RCU by the > > premature call to schedule_work(). > > Right. And that want's to be fixed, not hacked around by silencing RCU.
Fair enough!
I have updated my commit to indicate yours and Frederic's discomfort with it and marked it as not intended for upstream. If we get an alternative fix shortly, I will drop my commit -- but failing that at some point I will of course start pushing this patch again.
Thanx, Paul
> Peter???? > > Thanks, > > tglx >
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