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Subject: printk: Make rt aware
From: Thomas Gleixner <tglx@linutronix.de>
Date: Wed, 19 Sep 2012 14:50:37 +0200
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.9/older/patches-4.9.20-rt16.tar.xz
Drop the lock before calling the console driver and do not disable
interrupts while printing to a serial console.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
kernel/printk/printk.c | 25 +++++++++++++++++++++++--
1 file changed, 23 insertions(+), 2 deletions(-)
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -1628,6 +1628,7 @@ static void call_console_drivers(int lev
if (!console_drivers)
return;
+ migrate_disable();
for_each_console(con) {
if (exclusive_console && con != exclusive_console)
continue;
@@ -1643,6 +1644,7 @@ static void call_console_drivers(int lev
else
con->write(con, text, len);
}
+ migrate_enable();
}
/*
@@ -1951,13 +1953,23 @@ asmlinkage int vprintk_emit(int facility
/* If called from the scheduler, we can not call up(). */
if (!in_sched) {
+ int may_trylock = 1;
+
lockdep_off();
+#ifdef CONFIG_PREEMPT_RT_FULL
+ /*
+ * we can't take a sleeping lock with IRQs or preeption disabled
+ * so we can't print in these contexts
+ */
+ if (!(preempt_count() == 0 && !irqs_disabled()))
+ may_trylock = 0;
+#endif
/*
* Try to acquire and then immediately release the console
* semaphore. The release will print out buffers and wake up
* /dev/kmsg and syslog() users.
*/
- if (console_trylock())
+ if (may_trylock && console_trylock())
console_unlock();
lockdep_on();
}
@@ -2349,11 +2361,16 @@ static void console_cont_flush(char *tex
goto out;
len = cont_print_text(text, size);
+#ifdef CONFIG_PREEMPT_RT_FULL
+ raw_spin_unlock_irqrestore(&logbuf_lock, flags);
+ call_console_drivers(cont.level, NULL, 0, text, len);
+#else
raw_spin_unlock(&logbuf_lock);
stop_critical_timings();
call_console_drivers(cont.level, NULL, 0, text, len);
start_critical_timings();
local_irq_restore(flags);
+#endif
return;
out:
raw_spin_unlock_irqrestore(&logbuf_lock, flags);
@@ -2477,13 +2494,17 @@ void console_unlock(void)
console_idx = log_next(console_idx);
console_seq++;
console_prev = msg->flags;
+#ifdef CONFIG_PREEMPT_RT_FULL
+ raw_spin_unlock_irqrestore(&logbuf_lock, flags);
+ call_console_drivers(level, ext_text, ext_len, text, len);
+#else
raw_spin_unlock(&logbuf_lock);
stop_critical_timings(); /* don't trace print latency */
call_console_drivers(level, ext_text, ext_len, text, len);
start_critical_timings();
local_irq_restore(flags);
-
+#endif
if (do_cond_resched)
cond_resched();
}
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