| From | John Ogness <> | Subject | [PATCH printk v3 20/40] printk: __pr_flush: use srcu console list iterator | Date | Mon, 7 Nov 2022 15:22:18 +0106 |
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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 <john.ogness@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> --- kernel/printk/printk.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index ec50777d0301..d8ccb7b523e2 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -3480,6 +3480,7 @@ 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; @@ -3490,9 +3491,15 @@ 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)) @@ -3501,6 +3508,7 @@ 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 -- 2.30.2
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