Re: [PATCH RT] kernel/printk: Don't try to print from IRQ/NMI region
From: Steven Rostedt <rostedt@goodmis.org>
Date: 2016-05-27 14:12:56
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On Fri, 27 May 2016 15:58:12 +0200 Sebastian Andrzej Siewior [off-list ref] wrote:
quoted hunk ↗ jump to hunk
On -RT we try to acquire sleeping locks which might lead to warnings from lockdep or a warn_on() from spin_try_lock() (which is a rtmutex on RT). We don't print in general from a IRQ off region so we should not try this via console_unblank() / bust_spinlocks() as well. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> --- kernel/printk/printk.c | 10 ++++++++++ 1 file changed, 10 insertions(+)--- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c@@ -1502,6 +1502,11 @@ static void call_console_drivers(int lev if (!console_drivers) return; + if (IS_ENABLED(CONFIG_PREEMPT_RT_BASE)) { + if (in_irq() || in_nmi()) + return; + } +
We use to have a patch where a console could flag itself as atomic. That is, that it doesn't call any sleeping locks. What happened to that. IIRC, the video console was one such console. Otherwise, we lose out on backtraces in irq context. -- Steve
migrate_disable();
for_each_console(con) {
if (exclusive_console && con != exclusive_console)