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printk: nbcon: Flush new records on device_release()

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There may be new records that were added while a driver was
holding the nbcon context for non-printing purposes. These
new records must be flushed by the nbcon_device_release()
context because no other context will do it.

If boot consoles are registered, the legacy loop is used
(either direct or per irq_work) to handle the flushing.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-25-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
This commit is contained in:
John Ogness 2024-08-20 08:35:50 +02:06 committed by Petr Mladek
parent 70411bf8d2
commit 8ba77712a7
3 changed files with 23 additions and 1 deletions
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2
kernel/printk/internal.h
View File

@ -153,6 +153,8 @@ static inline bool console_is_usable(struct console *con, short flags) { return
#endif /* CONFIG_PRINTK */
extern bool have_boot_console;
extern struct printk_buffers printk_shared_pbufs;
/**

20
kernel/printk/nbcon.c
View File

@ -1326,10 +1326,30 @@ EXPORT_SYMBOL_GPL(nbcon_device_try_acquire);
void nbcon_device_release(struct console *con)
{
struct nbcon_context *ctxt = &ACCESS_PRIVATE(con, nbcon_device_ctxt);
int cookie;
if (!nbcon_context_exit_unsafe(ctxt))
return;
nbcon_context_release(ctxt);
/*
* This context must flush any new records added while the console
* was locked. The console_srcu_read_lock must be taken to ensure
* the console is usable throughout flushing.
*/
cookie = console_srcu_read_lock();
if (console_is_usable(con, console_srcu_read_flags(con)) &&
prb_read_valid(prb, nbcon_seq_read(con), NULL)) {
if (!have_boot_console) {
__nbcon_atomic_flush_pending_con(con, prb_next_reserve_seq(prb));
} else if (!is_printk_legacy_deferred()) {
if (console_trylock())
console_unlock();
} else {
printk_trigger_flush();
}
}
console_srcu_read_unlock(cookie);
}
EXPORT_SYMBOL_GPL(nbcon_device_release);

2
kernel/printk/printk.c
View File

@ -469,7 +469,7 @@ static DEFINE_MUTEX(syslog_lock);
* the console lock. This is because boot consoles and nbcon consoles may
* have mapped the same hardware.
*/
static bool have_boot_console;
bool have_boot_console;
#ifdef CONFIG_PRINTK
DECLARE_WAIT_QUEUE_HEAD(log_wait);