linux-toradex.git/kernel/rcu/tree.c, branch v4.16-rc6

Merge branches 'cond_resched.2017.12.04a', 'dyntick.2017.11.28a', 'fixes.2017.12.11a', 'srbd.2017.12.05a' and 'torture.2017.12.11a' into HEAD

2017-12-11T17:21:58+00:00

cond_resched.2017.12.04a: Convert cond_resched_rcu_qs() to cond_resched()
dyntick.2017.11.28a: Make RCU dynticks handle interrupts from NMI
fixes.2017.12.11a: Miscellaneous fixes
srbd.2017.12.05a: Remove now-redundant smp_read_barrier_depends()
torture.2017.12.11a: Torture-testing update

rcu: Add comment giving debug strategy for double call_rcu()

2017-12-11T17:17:39+00:00

The following statement has for some reason proven non-intuitive:

	WARN_ON_ONCE(rcu_segcblist_empty(&rdp->cblist) != (count == 0));

This commit therefore adds a comment that states that this warning
usually triggers in response to a double call_rcu(), which is sort
of like a double free.  The comment also suggests building with
CONFIG_DEBUG_OBJECTS_RCU_HEAD=y to track down the double call_rcu().

Reported-by: David Howells 
Signed-off-by: Paul E. McKenney

rcu: Simplify rcu_eqs_{enter,exit}() non-idle task debug code

2017-11-28T23:51:21+00:00

The code that checks for non-idle non-nohz_idle-usermode tasks invoking
rcu_eqs_enter() and rcu_eqs_exit() prints a considerable quantity of
helpful information.  However, these checks fire rarely, so the extra
complexity is no longer worth it.  This commit therefore replaces this
debug code with simple WARN_ON_ONCE() statements.

Signed-off-by: Paul E. McKenney

rcu: Fold rcu_eqs_exit_common() into rcu_eqs_exit()

2017-11-28T23:51:21+00:00

There is now only one call to rcu_eqs_exit_common() and there is no other
reason to keep it separate.  This commit therefore inlines it into its
sole call site, saving a few lines of code in the process.

Signed-off-by: Paul E. McKenney

rcu: Fold rcu_eqs_enter_common() into rcu_eqs_enter()

2017-11-28T23:51:20+00:00

There is now only one call to rcu_eqs_enter_common() and there is no other
reason to keep it separate.  This commit therefore inlines it into its
sole call site, saving a few lines of code in the process.

Signed-off-by: Paul E. McKenney

rcu: Avoid ->dynticks_nesting store tearing

2017-11-28T23:51:20+00:00

Although ->dynticks_nesting is updated only by process level, it is
accessed from hardirq to check for interrupt-from-idle quiescent states.
Store tearing is thus possible, so this commit applies WRITE_ONCE()
to ->dynticks_nesting stores.

Signed-off-by: Paul E. McKenney

rcu: Stop duplicating lockdep checks in RCU's idle-entry code

2017-11-28T23:51:19+00:00

The three RCU_LOCKDEP_WARN() calls in rcu_eqs_enter_common() are
redundant with other lockdep checks, so this commit removes them.

Signed-off-by: Paul E. McKenney

rcu: Add ->dynticks field to rcu_dyntick trace event

2017-11-28T23:51:19+00:00

Signed-off-by: Paul E. McKenney

rcu: Shrink ->dynticks_{nmi_,}nesting from long long to long

2017-11-28T23:51:18+00:00

Because the ->dynticks_nesting field now only contains the process-based
nesting level instead of a value encoding both the process nesting level
and the irq "nesting" level, we no longer need a long long, even on
32-bit systems.  This commit therefore changes both the ->dynticks_nesting
and ->dynticks_nmi_nesting fields to long.

Signed-off-by: Paul E. McKenney

rcu: Add tracing to irq/NMI dyntick-idle transitions

2017-11-28T23:51:18+00:00

Signed-off-by: Paul E. McKenney