[PATCH] powerpc: add support for preempt_auto

[Shrikanth Hegde]

Add PowerPC arch support for PREEMPT_AUTO by defining LAZY bits. 

Since PowerPC doesn't use generic exit to functions, Add 
NR_LAZY check in exit to user and exit to kernel from interrupt 
routines.  

Signed-off-by: Shrikanth Hegde <sshegde@xxxxxxxxxxxxx>
---
 arch/powerpc/Kconfig                   |  1 +
 arch/powerpc/include/asm/thread_info.h | 11 ++++++++++-
 arch/powerpc/kernel/interrupt.c        |  6 ++++--
 3 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 1c4be3373686..11e7008f5dd3 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -268,6 +268,7 @@ config PPC
 	select HAVE_PERF_EVENTS_NMI		if PPC64
 	select HAVE_PERF_REGS
 	select HAVE_PERF_USER_STACK_DUMP
+	select HAVE_PREEMPT_AUTO
 	select HAVE_REGS_AND_STACK_ACCESS_API
 	select HAVE_RELIABLE_STACKTRACE
 	select HAVE_RSEQ
diff --git a/arch/powerpc/include/asm/thread_info.h b/arch/powerpc/include/asm/thread_info.h
index 15c5691dd218..227b9273e2e9 100644
--- a/arch/powerpc/include/asm/thread_info.h
+++ b/arch/powerpc/include/asm/thread_info.h
@@ -118,10 +118,19 @@ void arch_setup_new_exec(void);
 #define TIF_POLLING_NRFLAG	19	/* true if poll_idle() is polling TIF_NEED_RESCHED */
 #define TIF_32BIT		20	/* 32 bit binary */
 
+#ifdef CONFIG_PREEMPT_AUTO
+#define TIF_NEED_RESCHED_LAZY	21	/* Lazy rescheduling */
+#endif
+
 /* as above, but as bit values */
 #define _TIF_SYSCALL_TRACE	(1<<TIF_SYSCALL_TRACE)
 #define _TIF_SIGPENDING		(1<<TIF_SIGPENDING)
 #define _TIF_NEED_RESCHED	(1<<TIF_NEED_RESCHED)
+
+#ifdef CONFIG_PREEMPT_AUTO
+#define _TIF_NEED_RESCHED_LAZY	(1 << TIF_NEED_RESCHED_LAZY)
+#endif
+
 #define _TIF_NOTIFY_SIGNAL	(1<<TIF_NOTIFY_SIGNAL)
 #define _TIF_POLLING_NRFLAG	(1<<TIF_POLLING_NRFLAG)
 #define _TIF_32BIT		(1<<TIF_32BIT)
@@ -144,7 +153,7 @@ void arch_setup_new_exec(void);
 #define _TIF_USER_WORK_MASK	(_TIF_SIGPENDING | _TIF_NEED_RESCHED | \
 				 _TIF_NOTIFY_RESUME | _TIF_UPROBE | \
 				 _TIF_RESTORE_TM | _TIF_PATCH_PENDING | \
-				 _TIF_NOTIFY_SIGNAL)
+				 _TIF_NOTIFY_SIGNAL | _TIF_NEED_RESCHED_LAZY)
 #define _TIF_PERSYSCALL_MASK	(_TIF_RESTOREALL|_TIF_NOERROR)
 
 /* Bits in local_flags */
diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c
index eca293794a1e..0c0b7010995a 100644
--- a/arch/powerpc/kernel/interrupt.c
+++ b/arch/powerpc/kernel/interrupt.c
@@ -185,7 +185,7 @@ interrupt_exit_user_prepare_main(unsigned long ret, struct pt_regs *regs)
 	ti_flags = read_thread_flags();
 	while (unlikely(ti_flags & (_TIF_USER_WORK_MASK & ~_TIF_RESTORE_TM))) {
 		local_irq_enable();
-		if (ti_flags & _TIF_NEED_RESCHED) {
+		if (ti_flags & (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY)) {
 			schedule();
 		} else {
 			/*
@@ -396,7 +396,9 @@ notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs)
 		/* Returning to a kernel context with local irqs enabled. */
 		WARN_ON_ONCE(!(regs->msr & MSR_EE));
 again:
-		if (IS_ENABLED(CONFIG_PREEMPT)) {
+
+		if ((IS_ENABLED(CONFIG_PREEMPT_AUTO) && IS_ENABLED(CONFIG_PREEMPTION)) ||
+		    (!IS_ENABLED(CONFIG_PREEMPT_AUTO) && IS_ENABLED(CONFIG_PREEMPT))) {
 			/* Return to preemptible kernel context */
 			if (unlikely(read_thread_flags() & _TIF_NEED_RESCHED)) {
 				if (preempt_count() == 0)
-- 
2.39.3