printk: use atomic updates for klogd work

BugLink: https://bugs.launchpad.net/bugs/1981864
[ Upstream commit 2ba3673d70178bf07fb75ff25c54bc478add4021 ]

The per-cpu @printk_pending variable can be updated from
sleepable contexts, such as:

  get_random_bytes()
    warn_unseeded_randomness()
      printk_deferred()
        defer_console_output()

and can be updated from interrupt contexts, such as:

  handle_irq_event_percpu()
    __irq_wake_thread()
      wake_up_process()
        try_to_wake_up()
          select_task_rq()
            select_fallback_rq()
              printk_deferred()
                defer_console_output()

and can be updated from NMI contexts, such as:

  vprintk()
    if (in_nmi()) defer_console_output()

Therefore the atomic variant of the updating functions must be used.

Replace __this_cpu_xchg() with this_cpu_xchg().
Replace __this_cpu_or() with this_cpu_or().

Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/87iltld4ue.fsf@jogness.linutronix.de
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 7aeb13542ce7afdbf8689718c96e9d9ed72299a3..e6a815a1cd76e9c6947c8fc9453526a73a870747 100644 (file)
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -3215,7 +3215,7 @@ static DEFINE_PER_CPU(int, printk_pending);
 
 static void wake_up_klogd_work_func(struct irq_work *irq_work)
 {
-       int pending = __this_cpu_xchg(printk_pending, 0);
+       int pending = this_cpu_xchg(printk_pending, 0);
 
        if (pending & PRINTK_PENDING_OUTPUT) {
                /* If trylock fails, someone else is doing the printing */
@@ -3249,7 +3249,7 @@ void defer_console_output(void)
                return;
 
        preempt_disable();
-       __this_cpu_or(printk_pending, PRINTK_PENDING_OUTPUT);
+       this_cpu_or(printk_pending, PRINTK_PENDING_OUTPUT);
        irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
        preempt_enable();
 }