From 5bfb5d690f36d316a5f3b4f7775fda996faa6b12 Mon Sep 17 00:00:00 2001 From: Nick Piggin Date: Tue, 8 Nov 2005 21:39:01 -0800 Subject: [PATCH] sched: disable preempt in idle tasks Run idle threads with preempt disabled. Also corrected a bugs in arm26's cpu_idle (make it actually call schedule()). How did it ever work before? Might fix the CPU hotplugging hang which Nigel Cunningham noted. We think the bug hits if the idle thread is preempted after checking need_resched() and before going to sleep, then the CPU offlined. After calling stop_machine_run, the CPU eventually returns from preemption and into the idle thread and goes to sleep. The CPU will continue executing previous idle and have no chance to call play_dead. By disabling preemption until we are ready to explicitly schedule, this bug is fixed and the idle threads generally become more robust. From: alexs PPC build fix From: Yoichi Yuasa MIPS build fix Signed-off-by: Nick Piggin Signed-off-by: Yoichi Yuasa Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/h8300/kernel/process.c | 28 +++++++++++++++------------- 1 file changed, 15 insertions(+), 13 deletions(-) (limited to 'arch/h8300') diff --git a/arch/h8300/kernel/process.c b/arch/h8300/kernel/process.c index 27f1fce..fe21adf 100644 --- a/arch/h8300/kernel/process.c +++ b/arch/h8300/kernel/process.c @@ -53,22 +53,18 @@ asmlinkage void ret_from_fork(void); #if !defined(CONFIG_H8300H_SIM) && !defined(CONFIG_H8S_SIM) void default_idle(void) { - while(1) { - if (!need_resched()) { - local_irq_enable(); - __asm__("sleep"); - local_irq_disable(); - } - schedule(); - } + local_irq_disable(); + if (!need_resched()) { + local_irq_enable(); + /* XXX: race here! What if need_resched() gets set now? */ + __asm__("sleep"); + } else + local_irq_enable(); } #else void default_idle(void) { - while(1) { - if (need_resched()) - schedule(); - } + cpu_relax(); } #endif void (*idle)(void) = default_idle; @@ -81,7 +77,13 @@ void (*idle)(void) = default_idle; */ void cpu_idle(void) { - idle(); + while (1) { + while (!need_resched()) + idle(); + preempt_enable_no_resched(); + schedule(); + preempt_disable(); + } } void machine_restart(char * __unused) -- cgit v1.1