[PATCH] RCU: add fake writers to rcutorture

[PATCH] RCU: add fake writers to rcutorture

rcutorture currently has one writer and an arbitrary number of readers.  To
better exercise some of the code paths in RCU implementations, add fake
writer threads which call the synchronize function for the RCU variant in a
loop, with a delay between calls to arrange for different numbers of
writers running in parallel.

[[email protected]: cleanup]
Acked-by: Paul McKenney <[email protected]>
Cc: Dipkanar Sarma <[email protected]>
Signed-off-by: Josh Triplett <[email protected]>
Signed-off-by: Adrian Bunk <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>