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/platforms/pseries/lpar.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) (limited to 'arch/powerpc/platforms/pseries/lpar.c') diff --git a/arch/powerpc/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c index 948e0e3b3547..7bc73af6c7b9 100644 --- a/arch/powerpc/platforms/pseries/lpar.c +++ b/arch/powerpc/platforms/pseries/lpar.c @@ -546,6 +546,13 @@ void __trace_hcall_entry(unsigned long opcode, unsigned long *args) unsigned long flags; unsigned int *depth; + /* + * We cannot call tracepoints inside RCU idle regions which + * means we must not trace H_CEDE. + */ + if (opcode == H_CEDE) + return; + local_irq_save(flags); depth = &__get_cpu_var(hcall_trace_depth); @@ -556,8 +563,6 @@ void __trace_hcall_entry(unsigned long opcode, unsigned long *args) (*depth)++; preempt_disable(); trace_hcall_entry(opcode, args); - if (opcode == H_CEDE) - rcu_idle_enter(); (*depth)--; out: @@ -570,6 +575,9 @@ void __trace_hcall_exit(long opcode, unsigned long retval, unsigned long flags; unsigned int *depth; + if (opcode == H_CEDE) + return; + local_irq_save(flags); depth = &__get_cpu_var(hcall_trace_depth); @@ -578,8 +586,6 @@ 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); preempt_enable(); (*depth)--; -- cgit v1.2.3