[PATCH printk v3 05/19] printk: Fail pr_flush() if before SYSTEM_SCHEDULING

[John Ogness]

A follow-up change adds pr_flush() to console unregistration.
However, with boot consoles unregistration can happen very
early if there are also regular consoles registering as well.
In this case the pr_flush() is not important because the
regular console manually flushes the boot consoles before
unregistering them.

Allow pr_flush() to fail if @system_state has not yet reached
SYSTEM_SCHEDULING. This avoids might_sleep() and msleep()
explosions that would otherwise occur.

Signed-off-by: John Ogness <john.ogness@xxxxxxxxxxxxx>
---
 kernel/printk/printk.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 641c2a8b0a09..39db56a32c5e 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -3946,6 +3946,10 @@ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre
 	u64 diff;
 	u64 seq;
 
+	/* Sorry, pr_flush() will not work this early. */
+	if (system_state < SYSTEM_SCHEDULING)
+		return false;
+
 	might_sleep();
 
 	seq = prb_next_reserve_seq(prb);
-- 
2.39.2