From: John Ogness Date: Wed, 16 Nov 2022 16:21:28 +0000 (+0106) Subject: printk: __pr_flush: use srcu console list iterator X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=eb7f1ed2509c6223d960a7d69644a8eb506b13d0;p=linux.git printk: __pr_flush: use srcu console list iterator Use srcu console list iteration for console list traversal. Document why the console_lock is still necessary. Note that this is a preparatory change for when console_lock no longer provides synchronization for the console list. Signed-off-by: John Ogness Reviewed-by: Petr Mladek Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20221116162152.193147-17-john.ogness@linutronix.de --- diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 13bc960c7aa53..abdbd3ffb0684 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -3561,6 +3561,7 @@ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre struct console *c; u64 last_diff = 0; u64 printk_seq; + int cookie; u64 diff; u64 seq; @@ -3571,9 +3572,15 @@ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre for (;;) { diff = 0; + /* + * Hold the console_lock to guarantee safe access to + * console->seq and to prevent changes to @console_suspended + * until all consoles have been processed. + */ console_lock(); - for_each_console(c) { + cookie = console_srcu_read_lock(); + for_each_console_srcu(c) { if (con && con != c) continue; if (!console_is_usable(c)) @@ -3582,6 +3589,7 @@ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre if (printk_seq < seq) diff += seq - printk_seq; } + console_srcu_read_unlock(cookie); /* * If consoles are suspended, it cannot be expected that they