From: John Ogness Date: Tue, 20 Aug 2024 08:35:50 +0206 Subject: [PATCH 24/54] printk: nbcon: Flush new records on device_release() Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.11/older/patches-6.11-rt7.tar.xz 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 Reviewed-by: Petr Mladek Link: https://lore.kernel.org/r/20240820063001.36405-25-john.ogness@linutronix.de Signed-off-by: Petr Mladek Signed-off-by: Sebastian Andrzej Siewior --- kernel/printk/internal.h | 2 ++ kernel/printk/nbcon.c | 20 ++++++++++++++++++++ kernel/printk/printk.c | 2 +- 3 files changed, 23 insertions(+), 1 deletion(-) --- a/kernel/printk/internal.h +++ b/kernel/printk/internal.h @@ -153,6 +153,8 @@ static inline bool console_is_usable(str #endif /* CONFIG_PRINTK */ +extern bool have_boot_console; + extern struct printk_buffers printk_shared_pbufs; /** --- a/kernel/printk/nbcon.c +++ b/kernel/printk/nbcon.c @@ -1326,10 +1326,30 @@ EXPORT_SYMBOL_GPL(nbcon_device_try_acqui 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); --- 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);