printk: nbcon: Flush new records on device_release()

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>

diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h
index 84706c1c934b25355805e62d0865713f3eb071f7..7679e18f24b34582d714682988c8d85f3a979b39 100644 (file)
--- a/kernel/printk/internal.h
+++ b/kernel/printk/internal.h
@@ -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;
 
 /**

diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c
index d09c084c9af4ab0f8a5559f3b5290f9f77c42953..269aeed1806493aca68a61b8c303696e0211ce27 100644 (file)
--- a/kernel/printk/nbcon.c
+++ b/kernel/printk/nbcon.c
@@ -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);

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index f08bf5e82fc732cde8a87e1abe1a040f9625b4e6..7c9f8f6e173877c7fb6686dc2237f71e97235b5b 100644 (file)
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -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);