The patch titled
Subject: stop_machine: make stop_machine safe and efficient to call early
has been added to the -mm tree. Its filename is
stop_machine-make-stop_machine-safe-and-efficient-to-call-early.patch
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------------------------------------------------------
From: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
Subject: stop_machine: make stop_machine safe and efficient to call early
Make stop_machine() safe to call early in boot, before SMP has been set
up, by simply calling the callback function directly if there's only one
CPU online.
[ Fixes from AKPM:
- add comment
- local_irq_flags, not save_flags
- also call hard_irq_disable() for systems which need it
Tejun suggested using an explicit flag rather than just looking at
the online cpu count. ]
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Acked-by: Tejun Heo <tj@xxxxxxxxxx>
Cc: Tejun Heo <htejun@xxxxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxx>
---
kernel/stop_machine.c | 21 +++++++++++++++++++++
1 file changed, 21 insertions(+)
diff -puN kernel/stop_machine.c~stop_machine-make-stop_machine-safe-and-efficient-to-call-early kernel/stop_machine.c
--- a/kernel/stop_machine.c~stop_machine-make-stop_machine-safe-and-efficient-to-call-early
+++ a/kernel/stop_machine.c
@@ -41,6 +41,7 @@ struct cpu_stopper {
};
static DEFINE_PER_CPU(struct cpu_stopper, cpu_stopper);
+static bool stop_machine_initialized = false;
static void cpu_stop_init_done(struct cpu_stop_done *done, unsigned int nr_todo)
{
@@ -386,6 +387,8 @@ static int __init cpu_stop_init(void)
cpu_stop_cpu_callback(&cpu_stop_cpu_notifier, CPU_ONLINE, bcpu);
register_cpu_notifier(&cpu_stop_cpu_notifier);
+ stop_machine_initialized = true;
+
return 0;
}
early_initcall(cpu_stop_init);
@@ -485,6 +488,24 @@ int __stop_machine(int (*fn)(void *), vo
.num_threads = num_online_cpus(),
.active_cpus = cpus };
+ if (!stop_machine_initialized) {
+ /*
+ * Handle the case where stop_machine() is called early in boot
+ * before SMP startup.
+ */
+ unsigned long flags;
+ int ret;
+
+ WARN_ON_ONCE(smdata.num_threads != 1);
+
+ local_irq_save(flags);
+ hard_irq_disable();
+ ret = (*fn)(data);
+ local_irq_restore(flags);
+
+ return ret;
+ }
+
/* Set the initial state and stop all online cpus. */
set_state(&smdata, STOPMACHINE_PREPARE);
return stop_cpus(cpu_online_mask, stop_machine_cpu_stop, &smdata);
_
Subject: Subject: stop_machine: make stop_machine safe and efficient to call early
Patches currently in -mm which might be from jeremy.fitzhardinge@xxxxxxxxxx are
origin.patch
linux-next.patch
x86-paravirt-pte-updates-in-kunmap_atomic-need-to-be-synchronous-regardless-of-lazy_mmu-mode.patch
mm-avoid-null-pointer-access-in-vm_struct-via-proc-vmallocinfo.patch
stop_machine-make-stop_machine-safe-and-efficient-to-call-early.patch
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