On Wed, Jan 27, 2021 at 12:58:33AM +0900, Sergey Senozhatsky wrote:
> On (21/01/26 14:59), Qais Yousef wrote:
> > # [67628.388606] hrtimer: interrupt took 304720 ns
> > [67628.393546]
> > [67628.393550] =============================
> > [67628.393554] [ BUG: Invalid wait context ]
> > [67628.393557] 5.11.0-rc3-00019-g86be331946f7 #37 Not tainted
> > [67628.393560] -----------------------------
> > [67628.393563] sugov:0/192 is trying to lock:
> > [67628.393566] ffff000800b1d898 (&port_lock_key){-.-.}-{3:3}, at:
> > pl011_console_write+0x138/0x218
> > [67628.393581] other info that might help us debug this:
> > [67628.393584] context-{2:2}
> > [67628.393586] 4 locks held by sugov:0/192:
> > [67628.393589] #0: ffff0008059cb720
> > (&sg_policy->work_lock){+.+.}-{4:4}, at: sugov_work+0x58/0x88
> > [67628.393603] #1: ffff800015446f20 (prepare_lock){+.+.}-{4:4}, at:
> > clk_prepare_lock+0x34/0xb0
> > [67628.393618] #2: ffff8000152aaa60 (console_lock){+.+.}-{0:0}, at:
> > vprintk_emit+0x12c/0x310
> > [67628.393632] #3: ffff8000152aab88 (console_owner){-.-.}-{0:0}, at:
> > console_unlock+0x190/0x6d8
> > Did I miss something?
>
> printk() is not permitted to sleep/schedule/etc and it never does.
> Generally it should be OK to call it from IRQ (module recursion paths).
The report is that it is trying to acquire spin_lock() while holding
raw_spin_lock(), which is an invalid lock nesting.
Note that this is CONFIG_PROVE_RAW_LOCK_NESTING=y which specifically
checks for this.
On current (mainline) kernel configs this is not yet a problem, but the
moment we do land PREEMPT_RT this order will be problematic.
