printk: Allow printk_trigger_flush() to flush all types

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 <pmladek@suse.com>
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/stable/20251113160351.113031-2-john.ogness%40linutronix.de
Tested-by: Sherry Sun <sherry.sun@nxp.com>
Link: https://patch.msgid.link/20251113160351.113031-2-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>

diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c
index 558ef31779760340ce42608294d91d5401239f1d..73f315fd97a3e3e2fd2c03f41bd086d5ec6c1561 100644 (file)
--- a/kernel/printk/nbcon.c
+++ b/kernel/printk/nbcon.c
@@ -1849,7 +1849,7 @@ 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 5aee9ffb16b9a5e7bfadb0266a77bfa569e50e51..dc89239cf1b58cd0ef937b130ca37fff8b1a3cbe 100644 (file)
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -4567,9 +4567,30 @@ 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)