diff options
| author | Anton Blanchard <anton@samba.org> | 2012-01-09 14:29:15 +0000 |
|---|---|---|
| committer | Benjamin Herrenschmidt <benh@kernel.crashing.org> | 2012-01-11 11:54:20 +1100 |
| commit | a5ccfee05a439b803640e94584056204501db31c (patch) | |
| tree | 2545bab092fe62924d5ccba8920c137b1e771ba6 | |
| parent | 7b3480f8b701170c046e1ed362946f5f0d005e13 (diff) | |
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 <anton@samba.org>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
| -rw-r--r-- | arch/powerpc/kernel/idle.c | 12 | ||||
| -rw-r--r-- | arch/powerpc/platforms/pseries/lpar.c | 14 |
2 files changed, 12 insertions, 14 deletions
diff --git a/arch/powerpc/kernel/idle.c b/arch/powerpc/kernel/idle.c index 7c66ce13da8..0a48bf5db6c 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()) diff --git a/arch/powerpc/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c index 948e0e3b354..7bc73af6c7b 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)--; |