[PREEMPT_RT]: Using printk-rt-aware.patch in non-rt kernel
From: Sebastian Andrzej Siewior <hidden>
Date: 2018-07-27 09:05:37
Also in:
linux-rt-users, lkml
Subsystem:
printk, the rest · Maintainers:
Petr Mladek, Linus Torvalds
On 2018-07-26 23:38:05 [+0530], Pintu Kumar wrote:
quoted
quoted
Is there a way we can fix this issue on non-rt kernel?I would guess that a wakeup to klogd would fix it.Sorry, can you elaborate more about "wakeup to klogd". I wanted to try it and check.
Something like this should do the work.
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 179ad787a08c..411f9ed5f051 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c@@ -1927,6 +1927,8 @@ static size_t log_output(int facility, int level, enum log_flags lflags, const c return log_store(facility, level, lflags, 0, dict, dictlen, text, text_len); } +static void printk_flush_pending_output(void); + asmlinkage int vprintk_emit(int facility, int level, const char *dict, size_t dictlen, const char *fmt, va_list args)
@@ -2026,6 +2028,9 @@ asmlinkage int vprintk_emit(int facility, int level, */ if (may_trylock && console_trylock_spinning()) console_unlock(); + else if (!may_trylock) + printk_flush_pending_output(); + migrate_enable(); }
@@ -2987,6 +2992,13 @@ static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = { .flags = IRQ_WORK_LAZY, }; +static void printk_flush_pending_output(void) +{ + /* preemption or interrupts need to be disabled */ + __this_cpu_or(printk_pending, PRINTK_PENDING_OUTPUT); + irq_work_queue(this_cpu_ptr(&wake_up_klogd_work)); +} + void wake_up_klogd(void) { preempt_disable();
Sebastian