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x86/split_lock: Simplify reenabling

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When split_lock_mitigate is disabled, each CPU needs its own delayed_work
structure. They are used to reenable split lock detection after its
disabling. But delayed_work structure must be correctly initialized after
its allocation.

Current implementation uses deferred initialization that makes the
split lock handler code unclear. The code can be simplified a bit
if the initialization is moved to the appropriate initcall.

sld_setup() is called before setup_per_cpu_areas(), thus it can't be used
for this purpose, so introduce an independent initcall for
the initialization.

[ mingo: Simplified the 'work' assignment line a bit more. ]

Signed-off-by: Maksim Davydov <davydov-max@yandex-team.ru>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20250325085807.171885-1-davydov-max@yandex-team.ru
This commit is contained in:
Maksim Davydov 2025-03-25 11:58:07 +03:00 committed by Ingo Molnar
parent 2df0c02dab
commit 0e1ff67d16
1 changed files with 24 additions and 11 deletions
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35
arch/x86/kernel/cpu/bus_lock.c
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@ -200,6 +200,26 @@ static void __split_lock_reenable(struct work_struct *work)
*/
static DEFINE_PER_CPU(struct delayed_work, sl_reenable);
/*
* Per-CPU delayed_work can't be statically initialized properly because
* the struct address is unknown. Thus per-CPU delayed_work structures
* have to be initialized during kernel initialization and after calling
* setup_per_cpu_areas().
*/
static int __init setup_split_lock_delayed_work(void)
{
unsigned int cpu;
for_each_possible_cpu(cpu) {
struct delayed_work *work = per_cpu_ptr(&sl_reenable, cpu);
INIT_DELAYED_WORK(work, __split_lock_reenable);
}
return 0;
}
pure_initcall(setup_split_lock_delayed_work);
/*
* If a CPU goes offline with pending delayed work to re-enable split lock
* detection then the delayed work will be executed on some other CPU. That
@ -219,15 +239,16 @@ static int splitlock_cpu_offline(unsigned int cpu)
static void split_lock_warn(unsigned long ip)
{
struct delayed_work *work = NULL;
struct delayed_work *work;
int cpu;
unsigned int saved_sld_mitigate = READ_ONCE(sysctl_sld_mitigate);
if (!current->reported_split_lock)
pr_warn_ratelimited("#AC: %s/%d took a split_lock trap at address: 0x%lx\n",
current->comm, current->pid, ip);
current->reported_split_lock = 1;
if (sysctl_sld_mitigate) {
if (saved_sld_mitigate) {
/*
* misery factor #1:
* sleep 10ms before trying to execute split lock.
@ -240,18 +261,10 @@ static void split_lock_warn(unsigned long ip)
*/
if (down_interruptible(&buslock_sem) == -EINTR)
return;
work = &sl_reenable_unlock;
}
cpu = get_cpu();
if (!work) {
work = this_cpu_ptr(&sl_reenable);
/* Deferred initialization of per-CPU struct */
if (!work->work.func)
INIT_DELAYED_WORK(work, __split_lock_reenable);
}
work = saved_sld_mitigate ? &sl_reenable_unlock : per_cpu_ptr(&sl_reenable, cpu);
schedule_delayed_work_on(cpu, work, 2);
/* Disable split lock detection on this CPU to make progress */