Messages in this thread Patch in this message | | | From | John Ogness <> | Subject | [PATCH printk v1 13/13] console: introduce CON_MIGHT_SLEEP for vt | Date | Mon, 7 Feb 2022 20:49:23 +0106 |
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Deadlocks and the framebuffer console have been a recurring issue that is getting worse. Daniel Vetter suggested [0] that fbcon->write() should no longer be called from an atomic context.
Introduce a new console flag CON_MIGHT_SLEEP for a console driver to specify that it is only called from sleepable contexts. Set the fbcon to use this new flag.
[0] https://lore.kernel.org/all/YYuS1uNhxWOEX1Ci@phenom.ffwll.local
Signed-off-by: John Ogness <john.ogness@linutronix.de> --- drivers/tty/vt/vt.c | 2 +- include/linux/console.h | 1 + kernel/printk/printk.c | 2 ++ 3 files changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c index 7359c3e80d63..ab4712cc9327 100644 --- a/drivers/tty/vt/vt.c +++ b/drivers/tty/vt/vt.c @@ -3161,7 +3161,7 @@ static struct console vt_console_driver = { .write = vt_console_print, .device = vt_console_device, .unblank = unblank_screen, - .flags = CON_PRINTBUFFER, + .flags = CON_PRINTBUFFER|CON_MIGHT_SLEEP, .index = -1, }; #endif diff --git a/include/linux/console.h b/include/linux/console.h index c51c7f5507a5..ea52c56b3ff8 100644 --- a/include/linux/console.h +++ b/include/linux/console.h @@ -138,6 +138,7 @@ static inline int con_debug_leave(void) #define CON_BRL (32) /* Used for a braille device */ #define CON_EXTENDED (64) /* Use the extended output format a la /dev/kmsg */ #define CON_PAUSED (128) /* Sleep while console is locked */ +#define CON_MIGHT_SLEEP (256) /* Can only be called from sleepable context */ struct console { char name[16]; diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 086155578f10..b92ef67a5aa2 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -2836,6 +2836,8 @@ static bool console_flush_all(bool do_cond_resched, u64 *next_seq, bool *handove if (!console_is_usable(con)) continue; + if ((con->flags & CON_MIGHT_SLEEP) && !do_cond_resched) + continue; any_usable = true; if (con->flags & CON_EXTENDED) { -- 2.30.2
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