rcu: Make exit_rcu() more precise and consolidate
authorPaul E. McKenney <paul.mckenney@linaro.org>
Fri, 13 Apr 2012 19:54:22 +0000 (12:54 -0700)
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Wed, 2 May 2012 21:48:27 +0000 (14:48 -0700)
commit9dd8fb16c36178df2066387d2abd44d8b4dca8c8
tree330ac5704044c12bcc94ec6bf96dbb27d1057f5d
parent616c310e83b872024271c915c1b9ab505b9efad9
rcu: Make exit_rcu() more precise and consolidate

When running preemptible RCU, if a task exits in an RCU read-side
critical section having blocked within that same RCU read-side critical
section, the task must be removed from the list of tasks blocking a
grace period (perhaps the current grace period, perhaps the next grace
period, depending on timing).  The exit() path invokes exit_rcu() to
do this cleanup.

However, the current implementation of exit_rcu() needlessly does the
cleanup even if the task did not block within the current RCU read-side
critical section, which wastes time and needlessly increases the size
of the state space.  Fix this by only doing the cleanup if the current
task is actually on the list of tasks blocking some grace period.

While we are at it, consolidate the two identical exit_rcu() functions
into a single function.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Linus Torvalds <torvalds@linux-foundation.org>

Conflicts:

kernel/rcupdate.c
include/linux/rcupdate.h
include/linux/rcutiny.h
include/linux/rcutree.h
kernel/rcupdate.c
kernel/rcutiny_plugin.h
kernel/rcutree_plugin.h