From a7b152d5342c06e81ab0cf7d18345f69fa7e56b5 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 13 Oct 2011 19:05:12 -0700 Subject: [PATCH] powerpc: Tell RCU about idle after hcall tracing The PowerPC pSeries platform (CONFIG_PPC_PSERIES=y) enables hypervisor-call tracing for CONFIG_TRACEPOINTS=y kernels. One of the hypervisor calls that is traced is the H_CEDE call in the idle loop that tells the hypervisor that this OS instance no longer needs the current CPU. However, tracing uses RCU, so this combination of kernel configuration variables needs to avoid telling RCU about the current CPU's idleness until after the H_CEDE-entry tracing completes on the one hand, and must tell RCU that the the current CPU is no longer idle before the H_CEDE-exit tracing starts. In all other cases, it suffices to inform RCU of CPU idleness upon idle-loop entry and exit. This commit makes the required adjustments. Signed-off-by: Paul E. McKenney Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett --- arch/powerpc/kernel/idle.c | 16 ++++++++++++++-- arch/powerpc/platforms/pseries/lpar.c | 4 ++++ 2 files changed, 18 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/kernel/idle.c b/arch/powerpc/kernel/idle.c index 2e782a36d8f2..3cd73d1fc427 100644 --- a/arch/powerpc/kernel/idle.c +++ b/arch/powerpc/kernel/idle.c @@ -46,6 +46,12 @@ 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. */ @@ -56,7 +62,10 @@ void cpu_idle(void) set_thread_flag(TIF_POLLING_NRFLAG); while (1) { - tick_nohz_idle_enter_norcu(); + if (idle_uses_rcu) + tick_nohz_idle_enter(); + else + tick_nohz_idle_enter_norcu(); while (!need_resched() && !cpu_should_die()) { ppc64_runlatch_off(); @@ -93,7 +102,10 @@ void cpu_idle(void) HMT_medium(); ppc64_runlatch_on(); - tick_nohz_idle_exit_norcu(); + if (idle_uses_rcu) + tick_nohz_idle_exit(); + else + tick_nohz_idle_exit_norcu(); preempt_enable_no_resched(); if (cpu_should_die()) cpu_die(); diff --git a/arch/powerpc/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c index 27a49508b410..52d429be6c76 100644 --- a/arch/powerpc/platforms/pseries/lpar.c +++ b/arch/powerpc/platforms/pseries/lpar.c @@ -555,6 +555,8 @@ void __trace_hcall_entry(unsigned long opcode, unsigned long *args) (*depth)++; trace_hcall_entry(opcode, args); + if (opcode == H_CEDE) + rcu_idle_enter(); (*depth)--; out: @@ -575,6 +577,8 @@ void __trace_hcall_exit(long opcode, unsigned long retval, goto out; (*depth)++; + if (opcode == H_CEDE) + rcu_idle_exit(); trace_hcall_exit(opcode, retval, retbuf); (*depth)--;