[PATCH tip/core/rcu 15/26] alpha: Fix preemption handling in idle loop

From: Frederic Weisbecker <redacted>

cpu_idle() is called on the boot CPU by the init code with
preemption disabled. But the cpu_idle() function in alpha
doesn't handle this when it calls schedule() directly.

Fix it by converting it into schedule_preempt_disabled().

Also disable preemption before calling cpu_idle() from
secondary CPU entry code to stay consistent with this
state.

Signed-off-by: Frederic Weisbecker <redacted>
Cc: Richard Henderson <redacted>
Cc: Ivan Kokshaysky <redacted>
Cc: Matt Turner <mattst88@gmail.com>
Cc: alpha <redacted>
Cc: Paul E. McKenney <redacted>
Cc: Michael Cree <redacted>
---
 arch/alpha/kernel/process.c |    3 ++-
 arch/alpha/kernel/smp.c     |    1 +
 2 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/arch/alpha/kernel/process.c b/arch/alpha/kernel/process.c
index 153d3fc..eac5e01 100644
--- a/arch/alpha/kernel/process.c
+++ b/arch/alpha/kernel/process.c

@@ -56,7 +56,8 @@ cpu_idle(void)
 
 		while (!need_resched())
 			cpu_relax();
-		schedule();
+
+		schedule_preempt_disabled();
 	}
 }
 

diff --git a/arch/alpha/kernel/smp.c b/arch/alpha/kernel/smp.c
index 35ddc02..a41ad90 100644
--- a/arch/alpha/kernel/smp.c
+++ b/arch/alpha/kernel/smp.c

@@ -166,6 +166,7 @@ smp_callin(void)
 	DBGS(("smp_callin: commencing CPU %d current %p active_mm %p\n",
 	      cpuid, current, current->active_mm));
 
+	preempt_disable();
 	/* Do nothing.  */
 	cpu_idle();
 }

-- 
1.7.8

On Thu, Aug 30, 2012 at 02:05:32PM -0700, Paul E. McKenney wrote:

From: Frederic Weisbecker <redacted>

cpu_idle() is called on the boot CPU by the init code with
preemption disabled. But the cpu_idle() function in alpha
doesn't handle this when it calls schedule() directly.

Fix it by converting it into schedule_preempt_disabled().

Also disable preemption before calling cpu_idle() from
secondary CPU entry code to stay consistent with this
state.

Signed-off-by: Frederic Weisbecker <redacted>
Cc: Richard Henderson <redacted>
Cc: Ivan Kokshaysky <redacted>
Cc: Matt Turner <mattst88@gmail.com>
Cc: alpha <redacted>
Cc: Paul E. McKenney <redacted>
Cc: Michael Cree <redacted>

Reviewed-by: Josh Triplett <josh@joshtriplett.org>