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Date: Tue, 19 Jun 2012 14:14:20 +0200
From: Igor Mammedov <imammedo@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: prarit@...hat.com, oleg@...hat.com, rob@...dley.net,
tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
x86@...nel.org, luto@....edu, suresh.b.siddha@...el.com,
avi@...hat.com, imammedo@...hat.com, a.p.zijlstra@...llo.nl,
johnstul@...ibm.com, arjan@...ux.intel.com
Subject: [PATCH 1/2] x86: abort secondary CPU bring-up gracefully if do_boot_cpu timed out on cpu_callin_mask
Master CPU may timeout before cpu_callin_mask is set and cancel
booting CPU, but being onlined CPU still continues to boot, sets
cpu_active_mask (CPU_STARTING notifiers) and spins in
check_tsc_sync_target() for master cpu to arrive. Following attempt
to online another cpu hangs in stop_machine, initiated from here:
smp_callin ->
smp_store_cpu_info ->
identify_secondary_cpu ->
mtrr_ap_init -> set_mtrr_from_inactive_cpu
stop_machine waits on completion of stop_work on all CPUs from
cpu_active_mask including a failed CPU that spins in check_tsc_sync_target().
Issue could be fixed if being onlined CPU continues to boot and calls
notify_cpu_starting(cpuid) only when master CPU waits for it to
come online. If master CPU times out on cpu_callin_mask and goes via
cancel path, the being onlined CPU should gracefully shutdown itself.
Patch introduces cpu_may_complete_boot_mask to notify a being onlined
CPU that it may call notify_cpu_starting(cpuid) and continue to boot
when master CPU goes via normal boot path and going to wait till the
being onlined CPU completes its initialization.
normal boot sequence will look like:
master CPU1 being onlined CPU2
* wait for CPU2 in cpu_callin_mask
---------------------------------------------------------------------
* set CPU2 in cpu_callin_mask
* wait till CPU1 set CPU2 bit
in cpu_may_complete_boot_mask
---------------------------------------------------------------------
* set CPU2 bit in
cpu_may_complete_boot_mask
* return from do_boot_cpu() and
wait in
- check_tsc_sync_source() or
- while (!cpu_online(CPU2))
---------------------------------------------------------------------
* call notify_cpu_starting()
and continue CPU2 initialization
* mark itself as ONLINE
---------------------------------------------------------------------
* return to _cpu_up and call
cpu_notify(CPU_ONLINE, ...)
cancel/error path will look like:
master CPU1 being onlined CPU2
* time out on cpu_callin_mask
---------------------------------------------------------------------
* set CPU2 in cpu_callin_mask
* wait till CPU2 is set in
cpu_may_complete_boot_mask or
cleared in cpu_callout_mask
---------------------------------------------------------------------
* clear CPU2 in cpu_callout_mask
and return with error
---------------------------------------------------------------------
* do cleanups and play_dead()
Note:
It's safe for being onlined CPU to set cpu_callin_mask before calling
notify_cpu_starting() because master CPU may first wait for being booted
CPU in check_tsc_sync_source() and then it waits in native_cpu_up() till
being booted CPU comes online and only when being booted CPU sets cpu_online_mask
it will exit native_cpu_up() and then call CPU_ONLINE notifiers.
v3:
- added missing remove_siblinginfo() on 'die' error path.
- added explanation why it's ok to set cpu_callin_mask before calling
CPU_STARTING notifiers
- being booted CPU will wait for master CPU without timeouts
Signed-off-by: Igor Mammedov <imammedo@...hat.com>
---
arch/x86/include/asm/cpumask.h | 1 +
arch/x86/kernel/cpu/common.c | 2 ++
arch/x86/kernel/smpboot.c | 34 ++++++++++++++++++++++++++++++++--
3 files changed, 35 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/cpumask.h b/arch/x86/include/asm/cpumask.h
index 61c852f..eacd269 100644
--- a/arch/x86/include/asm/cpumask.h
+++ b/arch/x86/include/asm/cpumask.h
@@ -7,6 +7,7 @@ extern cpumask_var_t cpu_callin_mask;
extern cpumask_var_t cpu_callout_mask;
extern cpumask_var_t cpu_initialized_mask;
extern cpumask_var_t cpu_sibling_setup_mask;
+extern cpumask_var_t cpu_may_complete_boot_mask;
extern void setup_cpu_local_masks(void);
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 6b9333b..16984f1 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -48,6 +48,7 @@
cpumask_var_t cpu_initialized_mask;
cpumask_var_t cpu_callout_mask;
cpumask_var_t cpu_callin_mask;
+cpumask_var_t cpu_may_complete_boot_mask;
/* representing cpus for which sibling maps can be computed */
cpumask_var_t cpu_sibling_setup_mask;
@@ -59,6 +60,7 @@ void __init setup_cpu_local_masks(void)
alloc_bootmem_cpumask_var(&cpu_callin_mask);
alloc_bootmem_cpumask_var(&cpu_callout_mask);
alloc_bootmem_cpumask_var(&cpu_sibling_setup_mask);
+ alloc_bootmem_cpumask_var(&cpu_may_complete_boot_mask);
}
static void __cpuinit default_init(struct cpuinfo_x86 *c)
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 7bd8a08..95948b9 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -122,6 +122,8 @@ EXPORT_PER_CPU_SYMBOL(cpu_info);
atomic_t init_deasserted;
+static void remove_siblinginfo(int cpu);
+
/*
* Report back to the Boot Processor.
* Running on AP.
@@ -218,12 +220,37 @@ static void __cpuinit smp_callin(void)
set_cpu_sibling_map(raw_smp_processor_id());
wmb();
- notify_cpu_starting(cpuid);
-
/*
* Allow the master to continue.
*/
cpumask_set_cpu(cpuid, cpu_callin_mask);
+
+ /*
+ * Wait for signal from master CPU to continue or abort.
+ */
+ while (!cpumask_test_cpu(cpuid, cpu_may_complete_boot_mask) &&
+ cpumask_test_cpu(cpuid, cpu_callout_mask)) {
+ cpu_relax();
+ }
+
+ /* die if master cancelled cpu_up */
+ if (!cpumask_test_cpu(cpuid, cpu_may_complete_boot_mask))
+ goto die;
+
+ notify_cpu_starting(cpuid);
+ return;
+
+die:
+#ifdef CONFIG_HOTPLUG_CPU
+ numa_remove_cpu(cpuid);
+ remove_siblinginfo(cpuid);
+ clear_local_APIC();
+ /* was set by cpu_init() */
+ cpumask_clear_cpu(cpuid, cpu_initialized_mask);
+ cpumask_clear_cpu(cpuid, cpu_callin_mask);
+ play_dead();
+#endif
+ panic("%s: Failed to online CPU%d!\n", __func__, cpuid);
}
/*
@@ -752,6 +779,8 @@ static int __cpuinit do_boot_cpu(int apicid, int cpu, struct task_struct *idle)
}
if (cpumask_test_cpu(cpu, cpu_callin_mask)) {
+ /* Signal AP that it may continue to boot */
+ cpumask_set_cpu(cpu, cpu_may_complete_boot_mask);
print_cpu_msr(&cpu_data(cpu));
pr_debug("CPU%d: has booted.\n", cpu);
} else {
@@ -1225,6 +1254,7 @@ static void __ref remove_cpu_from_maps(int cpu)
cpumask_clear_cpu(cpu, cpu_callin_mask);
/* was set by cpu_init() */
cpumask_clear_cpu(cpu, cpu_initialized_mask);
+ cpumask_clear_cpu(cpu, cpu_may_complete_boot_mask);
numa_remove_cpu(cpu);
}
--
1.7.1
--
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