Re: [PATCH] lockdep: add lockdep_cleanup_dead_cpu()

From: Peter Zijlstra
Date: Mon Oct 30 2023 - 07:17:40 EST

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On Sat, Oct 28, 2023 at 12:14:02PM +0100, David Woodhouse wrote:
> From: David Woodhouse <dwmw@xxxxxxxxxxxx>
>
> Add a function to check that an offlone CPU left the tracing infrastructure
> in a sane state. The acpi_idle_play_dead() function was recently observed
> calling safe_halt() instead of raw_safe_halt(), which had the side-effect

Right, so all that is because the offline path needs noinstr, but nobody
got around to doing that :/

Very rought attempt below, will scream bloody murder on build...

vmlinux.o: warning: objtool: idle_task_exit+0x45: call to switch_mm() leaves .noinstr.text section
vmlinux.o: warning: objtool: acpi_idle_play_dead+0x40: call to trace_hardirqs_on() leaves .noinstr.text section
vmlinux.o: warning: objtool: cpuidle_play_dead+0x10: call to cpuidle_get_cpu_driver() leaves .noinstr.text section

The acpi_idle_play_dead() thing is your original issue. No quick ideas
on what to do with switch_mm(), ideally we put that before we kill RCU
dead.

---
arch/x86/include/asm/cpuid.h | 4 ++--
arch/x86/include/asm/smp.h | 4 +++-
arch/x86/kernel/process.c | 4 ++--
arch/x86/kernel/smpboot.c | 12 ++++++------
arch/x86/kernel/tboot.c | 9 +++++----
drivers/acpi/processor_idle.c | 2 +-
drivers/cpuidle/cpuidle.c | 5 +++--
kernel/cpu.c | 15 +++++++++++----
kernel/rcu/tree.c | 15 ++++++++++-----
kernel/sched/core.c | 4 ++--
kernel/sched/idle.c | 2 +-
11 files changed, 46 insertions(+), 30 deletions(-)

diff --git a/arch/x86/include/asm/cpuid.h b/arch/x86/include/asm/cpuid.h
index 9bee3e7bf973..8417d741ce59 100644
--- a/arch/x86/include/asm/cpuid.h
+++ b/arch/x86/include/asm/cpuid.h
@@ -27,8 +27,8 @@ static inline int have_cpuid_p(void)
return 1;
}
#endif
-static inline void native_cpuid(unsigned int *eax, unsigned int *ebx,
- unsigned int *ecx, unsigned int *edx)
+static __always_inline void native_cpuid(unsigned int *eax, unsigned int *ebx,
+ unsigned int *ecx, unsigned int *edx)
{
/* ecx is often an input as well as an output. */
asm volatile("cpuid"
diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
index 4fab2ed454f3..41e839afba77 100644
--- a/arch/x86/include/asm/smp.h
+++ b/arch/x86/include/asm/smp.h
@@ -85,9 +85,11 @@ static inline void __cpu_die(unsigned int cpu)
smp_ops.cpu_die(cpu);
}

-static inline void __noreturn play_dead(void)
+static __always_inline void __noreturn play_dead(void)
{
+ instrumentation_begin(); // noinstr doesn't do indirect
smp_ops.play_dead();
+ instrumentation_end();
BUG();
}

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index b6f4e8399fca..c26d8f2af7bb 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -754,7 +754,7 @@ static bool x86_idle_set(void)
}

#ifndef CONFIG_SMP
-static inline void __noreturn play_dead(void)
+static inline void __noreturn noinstr play_dead(void)
{
BUG();
}
@@ -766,7 +766,7 @@ void arch_cpu_idle_enter(void)
local_touch_nmi();
}

-void __noreturn arch_cpu_idle_dead(void)
+noinstr void __noreturn arch_cpu_idle_dead(void)
{
play_dead();
}
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 222d62e84cb3..74a926ddfac5 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1474,20 +1474,20 @@ int native_cpu_disable(void)
return 0;
}

-void play_dead_common(void)
+noinstr void play_dead_common(void)
{
idle_task_exit();

cpuhp_ap_report_dead();

- local_irq_disable();
+ lockdep_assert_irqs_disabled();
}

/*
* We need to flush the caches before going to sleep, lest we have
* dirty data in our caches when we come back up.
*/
-static inline void mwait_play_dead(void)
+static __always_inline void mwait_play_dead(void)
{
struct mwait_cpu_dead *md = this_cpu_ptr(&mwait_cpu_dead);
unsigned int eax, ebx, ecx, edx;
@@ -1597,7 +1597,7 @@ void smp_kick_mwait_play_dead(void)
}
}

-void __noreturn hlt_play_dead(void)
+void __noreturn noinstr hlt_play_dead(void)
{
if (__this_cpu_read(cpu_info.x86) >= 4)
wbinvd();
@@ -1610,7 +1610,7 @@ void __noreturn hlt_play_dead(void)
* native_play_dead() is essentially a __noreturn function, but it can't
* be marked as such as the compiler may complain about it.
*/
-void native_play_dead(void)
+noinstr void native_play_dead(void)
{
if (cpu_feature_enabled(X86_FEATURE_KERNEL_IBRS))
__update_spec_ctrl(0);
@@ -1629,7 +1629,7 @@ int native_cpu_disable(void)
return -ENOSYS;
}

-void native_play_dead(void)
+noinstr void native_play_dead(void)
{
BUG();
}
diff --git a/arch/x86/kernel/tboot.c b/arch/x86/kernel/tboot.c
index 4c1bcb6053fc..a8fb9a5a4e02 100644
--- a/arch/x86/kernel/tboot.c
+++ b/arch/x86/kernel/tboot.c
@@ -105,7 +105,7 @@ static struct mm_struct tboot_mm = {
.mmlist = LIST_HEAD_INIT(init_mm.mmlist),
};

-static inline void switch_to_tboot_pt(void)
+static __always_inline void switch_to_tboot_pt(void)
{
write_cr3(virt_to_phys(tboot_pg_dir));
}
@@ -193,7 +193,7 @@ static void add_mac_region(phys_addr_t start, unsigned long size)
}
}

-static int tboot_setup_sleep(void)
+static noinstr int tboot_setup_sleep(void)
{
int i;

@@ -224,7 +224,7 @@ static int tboot_setup_sleep(void)

#endif

-void tboot_shutdown(u32 shutdown_type)
+noinstr void tboot_shutdown(u32 shutdown_type)
{
void (*shutdown)(void);

@@ -240,9 +240,10 @@ void tboot_shutdown(u32 shutdown_type)
return;

/* if this is S3 then set regions to MAC */
- if (shutdown_type == TB_SHUTDOWN_S3)
+ if (shutdown_type == TB_SHUTDOWN_S3) {
if (tboot_setup_sleep())
return;
+ }

tboot->shutdown_type = shutdown_type;

diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index 3a34a8c425fe..ad13fe635204 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -583,7 +583,7 @@ static void __cpuidle acpi_idle_do_entry(struct acpi_processor_cx *cx)
* @dev: the target CPU
* @index: the index of suggested state
*/
-static int acpi_idle_play_dead(struct cpuidle_device *dev, int index)
+static noinstr int acpi_idle_play_dead(struct cpuidle_device *dev, int index)
{
struct acpi_processor_cx *cx = per_cpu(acpi_cstate[index], dev->cpu);

diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index 737a026ef58a..67e66646912e 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -60,7 +60,7 @@ bool cpuidle_not_available(struct cpuidle_driver *drv,
*
* Returns in case of an error or no driver
*/
-int cpuidle_play_dead(void)
+noinstr int cpuidle_play_dead(void)
{
struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
@@ -70,9 +70,10 @@ int cpuidle_play_dead(void)
return -ENODEV;

/* Find lowest-power state that supports long-term idle */
- for (i = drv->state_count - 1; i >= 0; i--)
+ for (i = drv->state_count - 1; i >= 0; i--) {
if (drv->states[i].enter_dead)
return drv->states[i].enter_dead(dev, i);
+ }

return -ENODEV;
}
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 1a189da3bdac..5ca00bac6650 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -297,7 +297,7 @@ enum cpuhp_sync_state {
* No synchronization point. Just update of the synchronization state, but implies
* a full barrier so that the AP changes are visible before the control CPU proceeds.
*/
-static inline void cpuhp_ap_update_sync_state(enum cpuhp_sync_state state)
+static __always_inline void cpuhp_ap_update_sync_state(enum cpuhp_sync_state state)
{
atomic_t *st = this_cpu_ptr(&cpuhp_state.ap_sync_state);

@@ -347,7 +347,7 @@ static inline void cpuhp_ap_update_sync_state(enum cpuhp_sync_state state) { }
*
* No synchronization point. Just update of the synchronization state.
*/
-void cpuhp_ap_report_dead(void)
+noinstr void cpuhp_ap_report_dead(void)
{
cpuhp_ap_update_sync_state(SYNC_STATE_DEAD);
}
@@ -1391,19 +1391,26 @@ static void cpuhp_complete_idle_dead(void *arg)
complete_ap_thread(st, false);
}

-void cpuhp_report_idle_dead(void)
+noinstr void cpuhp_report_idle_dead(void)
{
- struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
+ struct cpuhp_cpu_state *st;

+ instrumentation_begin();
+ st = this_cpu_ptr(&cpuhp_state);
BUG_ON(st->state != CPUHP_AP_OFFLINE);
rcu_report_dead(smp_processor_id());
+ // instrumentation_end(); // RCU is dead here
+
st->state = CPUHP_AP_IDLE_DEAD;
/*
* We cannot call complete after rcu_report_dead() so we delegate it
* to an online cpu.
+ *
+ * XXX strictly speaking this should be noinstr, there's no RCU anymore
*/
smp_call_function_single(cpumask_first(cpu_online_mask),
cpuhp_complete_idle_dead, st, 0);
+ instrumentation_end();
}

static int cpuhp_down_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index cb1caefa8bd0..6c577a6d3581 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -4474,13 +4474,17 @@ void rcu_cpu_starting(unsigned int cpu)
* from the outgoing CPU rather than from the cpuhp_step mechanism.
* This is because this function must be invoked at a precise location.
*/
-void rcu_report_dead(unsigned int cpu)
+noinstr void rcu_report_dead(unsigned int cpu)
{
- unsigned long flags, seq_flags;
+ unsigned long flags;
unsigned long mask;
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */

+ lockdep_assert_irqs_disabled();
+
+ instrumentation_begin();
+
// Do any dangling deferred wakeups.
do_nocb_deferred_wakeup(rdp);

@@ -4488,7 +4492,7 @@ void rcu_report_dead(unsigned int cpu)

/* Remove outgoing CPU from mask in the leaf rcu_node structure. */
mask = rdp->grpmask;
- local_irq_save(seq_flags);
+
arch_spin_lock(&rcu_state.ofl_lock);
raw_spin_lock_irqsave_rcu_node(rnp, flags); /* Enforce GP memory-order guarantee. */
rdp->rcu_ofl_gp_seq = READ_ONCE(rcu_state.gp_seq);
@@ -4500,9 +4504,10 @@ void rcu_report_dead(unsigned int cpu)
raw_spin_lock_irqsave_rcu_node(rnp, flags);
}
WRITE_ONCE(rnp->qsmaskinitnext, rnp->qsmaskinitnext & ~mask);
- raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
+ raw_spin_unlock_irqrestore_rcu_node(rnp, flags); // XXX RCU already dead ?!
arch_spin_unlock(&rcu_state.ofl_lock);
- local_irq_restore(seq_flags);
+
+ instrumentation_end();

rdp->cpu_started = false;
}
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 81885748871d..4447e75e9275 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -9371,7 +9371,7 @@ void sched_setnuma(struct task_struct *p, int nid)
* Ensure that the idle task is using init_mm right before its CPU goes
* offline.
*/
-void idle_task_exit(void)
+noinstr void idle_task_exit(void)
{
struct mm_struct *mm = current->active_mm;

@@ -9379,7 +9379,7 @@ void idle_task_exit(void)
BUG_ON(current != this_rq()->idle);

if (mm != &init_mm) {
- switch_mm(mm, &init_mm, current);
+ switch_mm(mm, &init_mm, current); // XXX bugger ! properly broken
finish_arch_post_lock_switch();
}

diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index 565f8374ddbb..bf39ee9e5334 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -75,7 +75,7 @@ static noinline int __cpuidle cpu_idle_poll(void)
void __weak arch_cpu_idle_prepare(void) { }
void __weak arch_cpu_idle_enter(void) { }
void __weak arch_cpu_idle_exit(void) { }
-void __weak __noreturn arch_cpu_idle_dead(void) { while (1); }
+void __weak __noreturn noinstr arch_cpu_idle_dead(void) { while (1); }
void __weak arch_cpu_idle(void)
{
cpu_idle_force_poll = 1;

Next message: Stephan Mueller: "Re: [PATCH 4/4] crypto: drbg - Remove SHA1 from drbg"
Previous message: Yang Jihong: "[PATCH 2/2] perf tools: Add the python_ext_build directory to .gitignore"
In reply to: kernel test robot: "Re: [PATCH v2] lockdep: add lockdep_cleanup_dead_cpu()"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]