Messages in this thread Patch in this message |  | | Date | Fri, 16 Dec 2022 21:17:59 -0800 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH] rcu: Fix opposite might_sleep() check in rcu_blocking_is_gp() |
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On Sat, Dec 17, 2022 at 02:44:47AM +0000, Zhang, Qiang1 wrote: > > On Thu, Dec 15, 2022 at 11:57:55AM +0800, Zqiang wrote: > > Currently, if the system is in the RCU_SCHEDULER_INACTIVE state, invoke > > synchronize_rcu_*() will implies a grace period and return directly, > > so there is no sleep action due to waiting for a grace period to end, > > but this might_sleep() check is the opposite. therefore, this commit > > puts might_sleep() check in the correct palce. > > > > Signed-off-by: Zqiang <qiang1.zhang@intel.com> > > > >Queued for testing and review, thank you! > > > >I was under the impression that might_sleep() did some lockdep-based > >checking, but I am unable to find it. If there really is such checking, > >that would be a potential argument for leaving this code as it is. > > > > > >__might_sleep > > __might_resched(file, line, 0) > > rcu_sleep_check() > > > >Does it refer to this rcu_sleep_check() ? > > > >If so, when in the RCU_SCHEDULER_INACTIVE state, the debug_lockdep_rcu_enabled() is always > >return false, so the RCU_LOCKDEP_WARN() also does not produce an actual warning. > > and when the system_state == SYSTEM_BOOTING, we just did rcu_sleep_check() and then return.
Very good, thank you!
Thoughts from others?
Thanx, Paul
> Thanks > Zqiang > > >Thanks > >Zqiang > > > > >But in the meantime, full speed ahead! ;-) > > > > Thanx, Paul > > > > --- > > kernel/rcu/tree.c | 5 +++-- > > 1 file changed, 3 insertions(+), 2 deletions(-) > > > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > > index ee8a6a711719..65f3dd2fd3ae 100644 > > --- a/kernel/rcu/tree.c > > +++ b/kernel/rcu/tree.c > > @@ -3379,9 +3379,10 @@ void __init kfree_rcu_scheduler_running(void) > > */ > > static int rcu_blocking_is_gp(void) > > { > > - if (rcu_scheduler_active != RCU_SCHEDULER_INACTIVE) > > + if (rcu_scheduler_active != RCU_SCHEDULER_INACTIVE) { > > + might_sleep(); > > return false; > > - might_sleep(); /* Check for RCU read-side critical section. */ > > + } > > return true; > > } > > > > -- > > 2.25.1 > >
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