From a5ccfee05a439b803640e94584056204501db31c Mon Sep 17 00:00:00 2001 From: Anton Blanchard Date: Mon, 9 Jan 2012 14:29:15 +0000 Subject: powerpc: Fix RCU idle and hcall tracing Tracepoints should not be called inside an rcu_idle_enter/rcu_idle_exit region. Since pSeries calls H_CEDE in the idle loop, we were violating this rule. commit a7b152d5342c (powerpc: Tell RCU about idle after hcall tracing) tried to work around it by delaying the rcu_idle_enter until after we called the hcall tracepoint, but there are a number of issues with it. The hcall tracepoint trampoline code is called conditionally when the tracepoint is enabled. If the tracepoint is not enabled we never call rcu_idle_enter. The idle_uses_rcu check was also done at compile time which breaks multiplatform builds. The simple fix is to avoid tracing H_CEDE and rely on other tracepoints and the hypervisor dispatch trace log to work out if we called H_CEDE. This fixes a hang during boot on pSeries. Signed-off-by: Anton Blanchard Acked-by: Paul E. McKenney Signed-off-by: Benjamin Herrenschmidt --- arch/powerpc/kernel/idle.c | 12 ++---------- 1 file changed, 2 insertions(+), 10 deletions(-) (limited to 'arch/powerpc/kernel/idle.c') diff --git a/arch/powerpc/kernel/idle.c b/arch/powerpc/kernel/idle.c index 7c66ce13da89..0a48bf5db6c8 100644 --- a/arch/powerpc/kernel/idle.c +++ b/arch/powerpc/kernel/idle.c @@ -50,12 +50,6 @@ static int __init powersave_off(char *arg) } __setup("powersave=off", powersave_off); -#if defined(CONFIG_PPC_PSERIES) && defined(CONFIG_TRACEPOINTS) -static const bool idle_uses_rcu = 1; -#else -static const bool idle_uses_rcu; -#endif - /* * The body of the idle task. */ @@ -67,8 +61,7 @@ void cpu_idle(void) set_thread_flag(TIF_POLLING_NRFLAG); while (1) { tick_nohz_idle_enter(); - if (!idle_uses_rcu) - rcu_idle_enter(); + rcu_idle_enter(); while (!need_resched() && !cpu_should_die()) { ppc64_runlatch_off(); @@ -106,8 +99,7 @@ void cpu_idle(void) HMT_medium(); ppc64_runlatch_on(); - if (!idle_uses_rcu) - rcu_idle_exit(); + rcu_idle_exit(); tick_nohz_idle_exit(); preempt_enable_no_resched(); if (cpu_should_die()) -- cgit v1.2.3