linux-kernel - Re: [ANNOUNCE] v5.14-rc4-rt4

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Message-ID: <20210804110057.chsvt7l5xpw7bo5r@linutronix.de>
Date:   Wed, 4 Aug 2021 13:00:57 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Daniel Wagner <wagi@...om.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-rt-users@...r.kernel.org,
        Steven Rostedt <rostedt@...dmis.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Jens Axboe <axboe@...nel.dk>
Subject: Re: [ANNOUNCE] v5.14-rc4-rt4

On 2021-08-04 12:48:05 [+0200], To Daniel Wagner wrote:
> On 2021-08-04 12:43:42 [+0200], To Daniel Wagner wrote:
> > Odd. Do you have a config for that, please?
> 
> No need.
> | [   90.202543] BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:35
> | [   90.202549] in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 2047, name: iou-wrk-2041
> | [   90.202555] CPU: 5 PID: 2047 Comm: iou-wrk-2041 Tainted: G        W         5.14.0-rc4-rt4+ #89
> | [   90.202561] Call Trace:
…
> | [   90.202588]  rt_spin_lock+0x19/0x70
> | [   90.202593]  ___slab_alloc+0xcb/0x7d0
…
> | [   90.202618]  kmem_cache_alloc_trace+0x79/0x1f0
> | [   90.202621]  io_wqe_dec_running.isra.0+0x98/0xe0
> | [   90.202625]  io_wq_worker_sleeping+0x37/0x50
> | [   90.202628]  schedule+0x30/0xd0
> 
> le look.

So this is due to commit
  685fe7feedb96 ("io-wq: eliminate the need for a manager thread")

introduced in the v5.13-rc1 merge window. The call chain is
  schedule()
   sched_submit_work()
    preempt_disable();
    io_wq_worker_sleeping()
      raw_spin_lock_irq(&worker->wqe->lock);
      io_wqe_dec_running(worker);
       io_queue_worker_create()
        kmalloc(sizeof(*cwd), GFP_ATOMIC);

The lock wqe::lock has been turned into a raw_spinlock_t in commit
   95da84659226d ("io_wq: Make io_wqe::lock a raw_spinlock_t")

after a careful analysis of the code at that time. This commit breaks
things. Is this really needed?

> > > Thanks,
> > > Daniel

Sebastian