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Subject: kdb: only use atomic consoles for output mirroring
From: John Ogness <john.ogness@linutronix.de>
Date: Fri Mar 19 14:57:31 2021 +0100
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.15/older/patches-5.15.3-rt21.tar.xz
From: John Ogness <john.ogness@linutronix.de>
Currently kdb uses the @oops_in_progress hack to mirror kdb output
to all active consoles from NMI context. Ignoring locks is unsafe.
Now that an NMI-safe atomic interfaces is available for consoles,
use that interface to mirror kdb output.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
kernel/debug/kdb/kdb_io.c | 18 ++++++------------
1 file changed, 6 insertions(+), 12 deletions(-)
---
--- a/kernel/debug/kdb/kdb_io.c
+++ b/kernel/debug/kdb/kdb_io.c
@@ -559,23 +559,17 @@ static void kdb_msg_write(const char *ms
cp++;
}
+ /* mirror output on atomic consoles */
for_each_console(c) {
if (!(c->flags & CON_ENABLED))
continue;
if (c == dbg_io_ops->cons)
continue;
- /*
- * Set oops_in_progress to encourage the console drivers to
- * disregard their internal spin locks: in the current calling
- * context the risk of deadlock is a bigger problem than risks
- * due to re-entering the console driver. We operate directly on
- * oops_in_progress rather than using bust_spinlocks() because
- * the calls bust_spinlocks() makes on exit are not appropriate
- * for this calling context.
- */
- ++oops_in_progress;
- c->write(c, msg, msg_len);
- --oops_in_progress;
+
+ if (!c->write_atomic)
+ continue;
+ c->write_atomic(c, msg, msg_len);
+
touch_nmi_watchdog();
}
}
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