5.4.44-rt27-rc1 stable review patch. If anyone has any objections, please let me know. ------------------ From: John Ogness <john.ogness@xxxxxxxxxxxxx> Even though the printk kthread is always preemptible, it is still not allowed to call cond_resched() from within console drivers. The task may become non-preemptible in the console driver call chain. For example, vt_console_print() takes a spinlock and then can call into fbcon_redraw(), which can conditionally invoke cond_resched(): |BUG: sleeping function called from invalid context at kernel/printk/printk.c:2322 |in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 177, name: printk |CPU: 0 PID: 177 Comm: printk Not tainted 5.6.2-00011-ga536059557f1d9 #1 |Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014 |Call Trace: | dump_stack+0x66/0x8b | ___might_sleep+0x102/0x120 | console_conditional_schedule+0x24/0x30 | fbcon_redraw+0x96/0x1c0 | fbcon_scroll+0x556/0xd70 | con_scroll+0x147/0x1e0 | lf+0x9e/0xb0 | vt_console_print+0x253/0x3d0 | printk_kthread_func+0x1d5/0x3b0 Disable cond_resched() for the call into the console drivers. Reported-by: kernel test robot <rong.a.chen@xxxxxxxxx> Signed-off-by: John Ogness <john.ogness@xxxxxxxxxxxxx> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx> --- kernel/printk/printk.c | 1 + 1 file changed, 1 insertion(+) diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 2affe95866a4..9600373bcf55 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -2746,6 +2746,7 @@ static int printk_kthread_func(void *data) &len, printk_time); console_lock(); + console_may_schedule = 0; call_console_drivers(master_seq, ext_text, ext_len, text, len, msg->level, msg->facility); if (len > 0 || ext_len > 0) -- 2.26.2
