From be8ba672cc5ae52e8a10ac8eddb89d88f66b3cab Mon Sep 17 00:00:00 2001 From: John Ogness Date: Thu, 13 Nov 2025 17:09:47 +0106 Subject: [PATCH] printk: Allow printk_trigger_flush() to flush all types commit d01ff281bd9b1bfeac9ab98ec8a9ee41da900d5e upstream. Currently printk_trigger_flush() only triggers legacy offloaded flushing, even if that may not be the appropriate method to flush for currently registered consoles. (The function predates the NBCON consoles.) Since commit 6690d6b52726 ("printk: Add helper for flush type logic") there is printk_get_console_flush_type(), which also considers NBCON consoles and reports all the methods of flushing appropriate based on the system state and consoles available. Update printk_trigger_flush() to use printk_get_console_flush_type() to appropriately flush registered consoles. Suggested-by: Petr Mladek Signed-off-by: John Ogness Reviewed-by: Petr Mladek Link: https://lore.kernel.org/stable/20251113160351.113031-2-john.ogness%40linutronix.de Tested-by: Sherry Sun Link: https://patch.msgid.link/20251113160351.113031-2-john.ogness@linutronix.de Signed-off-by: Petr Mladek Signed-off-by: Greg Kroah-Hartman --- kernel/printk/nbcon.c | 2 +- kernel/printk/printk.c | 23 ++++++++++++++++++++++- 2 files changed, 23 insertions(+), 2 deletions(-) diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c index da07c59f7aa2e..730d14f6cbc58 100644 --- a/kernel/printk/nbcon.c +++ b/kernel/printk/nbcon.c @@ -1856,7 +1856,7 @@ void nbcon_device_release(struct console *con) if (console_trylock()) console_unlock(); } else if (ft.legacy_offload) { - printk_trigger_flush(); + defer_console_output(); } } console_srcu_read_unlock(cookie); diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index e850c237b4ba9..b1c0d35cf3caa 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -4595,9 +4595,30 @@ void defer_console_output(void) __wake_up_klogd(PRINTK_PENDING_WAKEUP | PRINTK_PENDING_OUTPUT); } +/** + * printk_trigger_flush - Attempt to flush printk buffer to consoles. + * + * If possible, flush the printk buffer to all consoles in the caller's + * context. If offloading is available, trigger deferred printing. + * + * This is best effort. Depending on the system state, console states, + * and caller context, no actual flushing may result from this call. + */ void printk_trigger_flush(void) { - defer_console_output(); + struct console_flush_type ft; + + printk_get_console_flush_type(&ft); + if (ft.nbcon_atomic) + nbcon_atomic_flush_pending(); + if (ft.nbcon_offload) + nbcon_kthreads_wake(); + if (ft.legacy_direct) { + if (console_trylock()) + console_unlock(); + } + if (ft.legacy_offload) + defer_console_output(); } int vprintk_deferred(const char *fmt, va_list args) -- 2.47.3