diff options
| author | Marcos Paulo de Souza <mpdesouza@suse.com> | 2025-10-16 11:47:56 -0300 |
|---|---|---|
| committer | Petr Mladek <pmladek@suse.com> | 2025-10-24 12:55:10 +0200 |
| commit | 286b113d70007e932d18aa0acfce1a3f5b25d8d1 (patch) | |
| tree | 2339e47c4813329ea0f447ce25bb28bc47cb7424 /kernel/printk/nbcon.c | |
| parent | 49f7d3054e84617395a37a058251c81320a3614a (diff) | |
printk: nbcon: Allow KDB to acquire the NBCON context
KDB can interrupt any console to execute the "mirrored printing" at any
time, so add an exception to nbcon_context_try_acquire_direct to allow
to get the context if the current CPU is the same as kdb_printf_cpu.
This change will be necessary for the next patch, which fixes
kdb_msg_write to work with NBCON consoles by calling ->write_atomic on
such consoles. But to print it first needs to acquire the ownership of
the console, so nbcon_context_try_acquire_direct is fixed here.
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://patch.msgid.link/20251016-nbcon-kgdboc-v6-3-866aac60a80e@suse.com
[pmladek@suse.com: Fix compilation with !CONFIG_KGDB_KDB.]
Signed-off-by: Petr Mladek <pmladek@suse.com>
Diffstat (limited to 'kernel/printk/nbcon.c')
| -rw-r--r-- | kernel/printk/nbcon.c | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c index e1bf5409cb6b..5be018493909 100644 --- a/kernel/printk/nbcon.c +++ b/kernel/printk/nbcon.c @@ -10,6 +10,7 @@ #include <linux/export.h> #include <linux/init.h> #include <linux/irqflags.h> +#include <linux/kdb.h> #include <linux/kthread.h> #include <linux/minmax.h> #include <linux/panic.h> @@ -249,13 +250,16 @@ static int nbcon_context_try_acquire_direct(struct nbcon_context *ctxt, * since all non-panic CPUs are stopped during panic(), it * is safer to have them avoid gaining console ownership. * - * If this acquire is a reacquire (and an unsafe takeover + * One exception is when kdb has locked for printing on this CPU. + * + * Second exception is a reacquire (and an unsafe takeover * has not previously occurred) then it is allowed to attempt * a direct acquire in panic. This gives console drivers an * opportunity to perform any necessary cleanup if they were * interrupted by the panic CPU while printing. */ if (panic_on_other_cpu() && + !kdb_printf_on_this_cpu() && (!is_reacquire || cur->unsafe_takeover)) { return -EPERM; } |