Messages in this thread Patch in this message | | | From | John Ogness <> | Subject | [PATCH printk v5 19/40] printk: console_flush_on_panic: use srcu console list iterator | Date | Wed, 16 Nov 2022 17:27:31 +0106 |
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With SRCU it is now safe to traverse the console list, even if the console_trylock() failed. However, overwriting console->seq when console_trylock() failed is still an issue.
Switch to SRCU iteration and document remaining issue with console->seq.
Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> --- kernel/printk/printk.c | 21 +++++++++++---------- 1 file changed, 11 insertions(+), 10 deletions(-)
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index b4be3b08d909..1a805ebdfe94 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -3049,21 +3049,22 @@ void console_flush_on_panic(enum con_flush_mode mode) console_may_schedule = 0; if (mode == CONSOLE_REPLAY_ALL) { - struct hlist_node *tmp; struct console *c; + int cookie; u64 seq; seq = prb_first_valid_seq(prb); - /* - * This cannot use for_each_console() because it's not established - * that the current context has console locked and neither there is - * a guarantee that there is no concurrency in that case. - * - * Open code it for documentation purposes and pretend that - * it works. - */ - hlist_for_each_entry_safe(c, tmp, &console_list, node) + + cookie = console_srcu_read_lock(); + for_each_console_srcu(c) { + /* + * If the above console_trylock() failed, this is an + * unsynchronized assignment. But in that case, the + * kernel is in "hope and pray" mode anyway. + */ c->seq = seq; + } + console_srcu_read_unlock(cookie); } console_unlock(); } -- 2.30.2
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