Messages in this thread | | | Date | Thu, 26 May 2011 09:28:02 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [tip:core/rcu] Revert "rcu: Decrease memory-barrier usage based on semi-formal proof" |
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On Thu, May 26, 2011 at 08:08:26AM -0700, Yinghai Lu wrote: > On Wed, May 25, 2011 at 6:30 PM, Paul E. McKenney > <paulmck@linux.vnet.ibm.com> wrote: > > On Wed, May 25, 2011 at 06:13:10PM -0700, Paul E. McKenney wrote: > >> On Wed, May 25, 2011 at 03:49:25PM -0700, Yinghai Lu wrote: > >> > On 05/25/2011 03:34 PM, Paul E. McKenney wrote: > >> > > On Wed, May 25, 2011 at 03:15:50PM -0700, Yinghai Lu wrote: > >> > >>> There is a new branch yinghai.2011.05.24a on: > >> > >>> > >> > >>> git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-2.6-rcu.git > >> > >>> > >> > >>> Or will be as soon as kernel.org updates its mirrors. > >> > >>> > >> > >>> I am not sure I could call this "clean", but it does revert that commit > >> > >>> and 11 of the subsequent commits that depend on it. It does build, > >> > >>> and I will test it once my currently running tests complete. > >> > >> > >> > >> yes, with those revert, there is no delay in 10 times booting. > >> > > > >> > > Unfortunately, there are rcutorture test failures with the revert... > >> > > >> > confused. > >> > >> Given what I had to do to generate the revert, not exactly a surprise, > >> I am afraid. Just means that the resulting RCU sometimes fails to > >> wait for all pre-existing readers, and rcutorture catches it. > >> > >> > what is the next? > >> > >> 1. I send you a patch that I hope will fix the softlockup > >> you saw. I am testing this. > >> > >> 2. I am working on more detailed instrumentation, and will > >> send a patch on that. > >> > >> 3. If time allows, break down the operations RCU is doing > >> and test them in isolation. > >> > >> Other thoughts? > > > > And here is patch #1. Could you please try applying this on top of > > Peter Zijlstra's patch to see if it gets rid of the softlockups you saw? > > > > Thanx, Paul > > > > ------------------------------------------------------------------------ > > > > rcu: Start RCU kthreads in TASK_INTERRUPTIBLE state > > > > Upon creation, kthreads are in TASK_UNINTERRUPTIBLE state, which can > > result in softlockup warnings. Because some of RCU's kthreads can > > legitimately be idle indefinitely, start them in TASK_INTERRUPTIBLE > > state in order to avoid those warnings. > > Yes, it fixes the lock up warning.
Very good, I have added your Tested-by.
Thanx, Paul -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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