rcu: Fix RCU CPU stall detection in tiny implementation
rcu: Fix RCU CPU stall detection in tiny implementation

The tiny RCU CPU stall detection depends on *rcp->curtail not being
NULL. It is however a tail pointer and thus NULL by definition. Instead we
should check rcp->rcucblist for the presence of pending callbacks which
need to be processed. With this fix INFO about the stall is printed and
jiffies_stall (jiffies at next stall) correctly updated.

Note that the check for pending callback is necessary to avoid spurious
warnings if there are no pendings callbacks.

Signed-off-by: Miroslav Benes <cbfd8e8fabdd2f11e58abb6fa6436d3d90debaf4@suse.cz>
[ paulmck: Fused identical "if" statements, ported to -rcu. ]
Signed-off-by: Paul E. McKenney <1e0ce936bb9b355d257bf5790d2513c3f28be22b@linux.vnet.ibm.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs