[PATCH] sched: cleanup context switch locking

Instead of requiring architecture code to interact with the scheduler's
locking implementation, provide a couple of defines that can be used by the
architecture to request runqueue unlocked context switches, and ask for
interrupts to be enabled over the context switch.

Also replaces the "switch_lock" used by these architectures with an oncpu
flag (note, not a potentially slow bitflag).  This eliminates one bus
locked memory operation when context switching, and simplifies the
task_running function.

Signed-off-by: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 4 insertions, 10 deletions

diff --git a/include/asm-sparc64/system.h b/include/asm-sparc64/system.h
index fd12ca386f48..f9be2c5b4dc9 100644
--- a/include/asm-sparc64/system.h
+++ b/include/asm-sparc64/system.h
@@ -139,19 +139,13 @@ extern void __flushw_user(void);
 #define flush_user_windows flushw_user
 #define flush_register_windows flushw_all
 
-#define prepare_arch_switch(rq, next)           \
-do {    spin_lock(&(next)->switch_lock);        \
-        spin_unlock(&(rq)->lock);               \
+/* Don't hold the runqueue lock over context switch */
+#define __ARCH_WANT_UNLOCKED_CTXSW
+#define prepare_arch_switch(next)               \
+do {                                            \
         flushw_all();                           \
 } while (0)
 
-#define finish_arch_switch(rq, prev)            \
-do {    spin_unlock_irq(&(prev)->switch_lock);  \
-} while (0)
-
-#define task_running(rq, p) \
-        ((rq)->curr == (p) || spin_is_locked(&(p)->switch_lock))
-
         /* See what happens when you design the chip correctly?
          *
          * We tell gcc we clobber all non-fixed-usage registers except