diff options
| author | John Ogness <john.ogness@linutronix.de> | 2022-04-21 23:28:40 +0206 |
|---|---|---|
| committer | Petr Mladek <pmladek@suse.com> | 2022-04-22 21:30:57 +0200 |
| commit | 5341b93dea8c39d7612f7a227015d4b1d5cf30db (patch) | |
| tree | 720691f7d680899dc1f1673487a625cb2c9409e2 /kernel | |
| parent | 938ba4084abcf6fdd21d9078513c52f8fb9b00d0 (diff) | |
printk: wake waiters for safe and NMI contexts
When printk() is called from safe or NMI contexts, it will directly
store the record (vprintk_store()) and then defer the console output.
However, defer_console_output() only causes console printing and does
not wake any waiters of new records.
Wake waiters from defer_console_output() so that they also are aware
of the new records from safe and NMI contexts.
Fixes: 03fc7f9c99c1 ("printk/nmi: Prevent deadlock when accessing the main log buffer in NMI")
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20220421212250.565456-6-john.ogness@linutronix.de
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/printk/printk.c | 28 |
1 files changed, 16 insertions, 12 deletions
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index e23357002648..7bb148a1debb 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -754,7 +754,7 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf, * prepare_to_wait_event() pairs with the full memory barrier * within wq_has_sleeper(). * - * This pairs with wake_up_klogd:A. + * This pairs with __wake_up_klogd:A. */ ret = wait_event_interruptible(log_wait, prb_read_valid(prb, @@ -1532,7 +1532,7 @@ static int syslog_print(char __user *buf, int size) * prepare_to_wait_event() pairs with the full memory barrier * within wq_has_sleeper(). * - * This pairs with wake_up_klogd:A. + * This pairs with __wake_up_klogd:A. */ len = wait_event_interruptible(log_wait, prb_read_valid(prb, seq, NULL)); /* LMM(syslog_print:A) */ @@ -3332,7 +3332,7 @@ static void wake_up_klogd_work_func(struct irq_work *irq_work) static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = IRQ_WORK_INIT_LAZY(wake_up_klogd_work_func); -void wake_up_klogd(void) +static void __wake_up_klogd(int val) { if (!printk_percpu_data_ready()) return; @@ -3349,22 +3349,26 @@ void wake_up_klogd(void) * * This pairs with devkmsg_read:A and syslog_print:A. */ - if (wq_has_sleeper(&log_wait)) { /* LMM(wake_up_klogd:A) */ - this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP); + if (wq_has_sleeper(&log_wait) || /* LMM(__wake_up_klogd:A) */ + (val & PRINTK_PENDING_OUTPUT)) { + this_cpu_or(printk_pending, val); irq_work_queue(this_cpu_ptr(&wake_up_klogd_work)); } preempt_enable(); } -void defer_console_output(void) +void wake_up_klogd(void) { - if (!printk_percpu_data_ready()) - return; + __wake_up_klogd(PRINTK_PENDING_WAKEUP); +} - preempt_disable(); - this_cpu_or(printk_pending, PRINTK_PENDING_OUTPUT); - irq_work_queue(this_cpu_ptr(&wake_up_klogd_work)); - preempt_enable(); +void defer_console_output(void) +{ + /* + * New messages may have been added directly to the ringbuffer + * using vprintk_store(), so wake any waiters as well. + */ + __wake_up_klogd(PRINTK_PENDING_WAKEUP | PRINTK_PENDING_OUTPUT); } void printk_trigger_flush(void) |