[PATCH 5.10-rt] printk: ignore that console preempted by irq/softirq

[xu.xin16]

From: xu xin <xu.xin16@xxxxxxxxxx>

When we're in the unpreemptible context on the same cpu with which the
thread of console locates on, we should ignore this console for
pr_flush, because it's a vain and always lead to timeout until the console
thread get cpu resource.

Fixes: e65be5f4dc3ed("printk: Update John Ogness' printk series")
Signed-off-by: xu xin <xu.xin16@xxxxxxxxxx>
Cc: Zhang Yunkai <zhang.yunkai@xxxxxxxxxx>
---
kernel/printk/printk.c | 8 ++++++++
1 file changed, 8 insertions(+)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 7f27cfee283e..faab85dd4439 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -3735,6 +3735,14 @@ bool pr_flush(int timeout_ms, bool reset_on_progress)
diff = 0;

for_each_console(con) {
+ /*
+ * When we're in the unpreemptible context on the same cpu
+ * with which the thread of console locates on, we should
+ * ignore this console, because it's a vain.
+ */
+ if (!preemptible() && con->thread &&
+ task_cpu(con->thread) == smp_processor_id())
+ continue;
if (!(con->flags & CON_ENABLED))
continue;
printk_seq = read_console_seq(con);
--
2.15.2