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Date: Tue, 10 Aug 2021 11:42:54 +0200 From: Marco Elver <elver@...gle.com> To: Clark Williams <williams@...hat.com> Cc: Sebastian Andrzej Siewior <bigeasy@...utronix.de>, Thomas Gleixner <tglx@...utronix.de>, Steven Rostedt <rostedt@...dmis.org>, Dmitry Vyukov <dvyukov@...gle.com>, Andrey Konovalov <andreyknvl@...il.com>, kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org Subject: Re: [PATCH PREEMPT_RT] kcov: fix locking splat from kcov_remote_start() On Mon, 9 Aug 2021 at 22:59, Clark Williams <williams@...hat.com> wrote: > Saw the following splat on 5.14-rc4-rt5 with: > > CONFIG_KCOV=y > CONFIG_KCOV_INSTRUMENT_ALL=y > CONFIG_KCOV_IRQ_AREA_SIZE=0x40000 > CONFIG_RUNTIME_TESTING_MENU=y > > kernel: ehci-pci 0000:00:1d.0: USB 2.0 started, EHCI 1.00 > kernel: BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:35 > kernel: in_atomic(): 0, irqs_disabled(): 1, non_block: 0, pid: 34, name: ksoftirqd/3 > kernel: 4 locks held by ksoftirqd/3/34: > kernel: #0: ffff944376d989f8 ((softirq_ctrl.lock).lock){+.+.}-{2:2}, at: __local_bh_disable_ip+0xe0/0x190 > kernel: #1: ffffffffbbfb61e0 (rcu_read_lock){....}-{1:2}, at: rt_spin_lock+0x5/0xd0 > kernel: #2: ffffffffbbfb61e0 (rcu_read_lock){....}-{1:2}, at: __local_bh_disable_ip+0xbd/0x190 > kernel: #3: ffffffffbc086518 (kcov_remote_lock){....}-{2:2}, at: kcov_remote_start+0x119/0x4a0 > kernel: irq event stamp: 4653 > kernel: hardirqs last enabled at (4652): [<ffffffffbafb85ce>] _raw_spin_unlock_irqrestore+0x6e/0x80 > kernel: hardirqs last disabled at (4653): [<ffffffffba2517c8>] kcov_remote_start+0x298/0x4a0 > kernel: softirqs last enabled at (4638): [<ffffffffba110a5b>] run_ksoftirqd+0x9b/0x100 > kernel: softirqs last disabled at (4644): [<ffffffffba149f12>] smpboot_thread_fn+0x2b2/0x410 > kernel: CPU: 3 PID: 34 Comm: ksoftirqd/3 Not tainted 5.14.0-rc4-rt5+ #3 > kernel: Hardware name: /NUC5i7RYB, BIOS RYBDWi35.86A.0359.2016.0906.1028 09/06/2016 > kernel: Call Trace: > kernel: dump_stack_lvl+0x7a/0x9b > kernel: ___might_sleep.cold+0xf3/0x107 > kernel: rt_spin_lock+0x3a/0xd0 > kernel: ? kcov_remote_start+0x119/0x4a0 > kernel: kcov_remote_start+0x119/0x4a0 > kernel: ? led_trigger_blink_oneshot+0x83/0xa0 > kernel: __usb_hcd_giveback_urb+0x161/0x1e0 > kernel: usb_giveback_urb_bh+0xb6/0x110 > kernel: tasklet_action_common.constprop.0+0xe8/0x110 > kernel: __do_softirq+0xe2/0x525 > kernel: ? smpboot_thread_fn+0x31/0x410 > kernel: run_ksoftirqd+0x8c/0x100 > kernel: smpboot_thread_fn+0x2b2/0x410 > kernel: ? smpboot_register_percpu_thread+0x130/0x130 > kernel: kthread+0x1de/0x210 > kernel: ? set_kthread_struct+0x60/0x60 > kernel: ret_from_fork+0x22/0x30 > kernel: usb usb1: New USB device found, idVendor=1d6b, idProduct=0002, bcdDevice= 5.14 > > > Change kcov_remote_lock from regular spinlock_t to raw_spinlock_t so that > we don't get "sleeping function called from invalid context" on PREEMPT_RT kernel. > > Signed-off-by: Clark Williams <williams@...hat.com> Reviewed-by: Marco Elver <elver@...gle.com> Indeed, most other debugging tools are using raw_spinlock or arch_spinlock, I guess KCOV was still lagging behind. Should this go into mainline? > --- > kernel/kcov.c | 28 ++++++++++++++-------------- > 1 file changed, 14 insertions(+), 14 deletions(-) > > diff --git a/kernel/kcov.c b/kernel/kcov.c > index 80bfe71bbe13..60f903f8a46c 100644 > --- a/kernel/kcov.c > +++ b/kernel/kcov.c > @@ -82,7 +82,7 @@ struct kcov_remote { > struct hlist_node hnode; > }; > > -static DEFINE_SPINLOCK(kcov_remote_lock); > +static DEFINE_RAW_SPINLOCK(kcov_remote_lock); > static DEFINE_HASHTABLE(kcov_remote_map, 4); > static struct list_head kcov_remote_areas = LIST_HEAD_INIT(kcov_remote_areas); > > @@ -375,7 +375,7 @@ static void kcov_remote_reset(struct kcov *kcov) > struct hlist_node *tmp; > unsigned long flags; > > - spin_lock_irqsave(&kcov_remote_lock, flags); > + raw_spin_lock_irqsave(&kcov_remote_lock, flags); > hash_for_each_safe(kcov_remote_map, bkt, tmp, remote, hnode) { > if (remote->kcov != kcov) > continue; > @@ -384,7 +384,7 @@ static void kcov_remote_reset(struct kcov *kcov) > } > /* Do reset before unlock to prevent races with kcov_remote_start(). */ > kcov_reset(kcov); > - spin_unlock_irqrestore(&kcov_remote_lock, flags); > + raw_spin_unlock_irqrestore(&kcov_remote_lock, flags); > } > > static void kcov_disable(struct task_struct *t, struct kcov *kcov) > @@ -638,18 +638,18 @@ static int kcov_ioctl_locked(struct kcov *kcov, unsigned int cmd, > kcov->t = t; > kcov->remote = true; > kcov->remote_size = remote_arg->area_size; > - spin_lock_irqsave(&kcov_remote_lock, flags); > + raw_spin_lock_irqsave(&kcov_remote_lock, flags); > for (i = 0; i < remote_arg->num_handles; i++) { > if (!kcov_check_handle(remote_arg->handles[i], > false, true, false)) { > - spin_unlock_irqrestore(&kcov_remote_lock, > + raw_spin_unlock_irqrestore(&kcov_remote_lock, > flags); > kcov_disable(t, kcov); > return -EINVAL; > } > remote = kcov_remote_add(kcov, remote_arg->handles[i]); > if (IS_ERR(remote)) { > - spin_unlock_irqrestore(&kcov_remote_lock, > + raw_spin_unlock_irqrestore(&kcov_remote_lock, > flags); > kcov_disable(t, kcov); > return PTR_ERR(remote); > @@ -658,7 +658,7 @@ static int kcov_ioctl_locked(struct kcov *kcov, unsigned int cmd, > if (remote_arg->common_handle) { > if (!kcov_check_handle(remote_arg->common_handle, > true, false, false)) { > - spin_unlock_irqrestore(&kcov_remote_lock, > + raw_spin_unlock_irqrestore(&kcov_remote_lock, > flags); > kcov_disable(t, kcov); > return -EINVAL; > @@ -666,14 +666,14 @@ static int kcov_ioctl_locked(struct kcov *kcov, unsigned int cmd, > remote = kcov_remote_add(kcov, > remote_arg->common_handle); > if (IS_ERR(remote)) { > - spin_unlock_irqrestore(&kcov_remote_lock, > + raw_spin_unlock_irqrestore(&kcov_remote_lock, > flags); > kcov_disable(t, kcov); > return PTR_ERR(remote); > } > t->kcov_handle = remote_arg->common_handle; > } > - spin_unlock_irqrestore(&kcov_remote_lock, flags); > + raw_spin_unlock_irqrestore(&kcov_remote_lock, flags); > /* Put either in kcov_task_exit() or in KCOV_DISABLE. */ > kcov_get(kcov); > return 0; > @@ -845,10 +845,10 @@ void kcov_remote_start(u64 handle) > return; > } > > - spin_lock(&kcov_remote_lock); > + raw_spin_lock(&kcov_remote_lock); > remote = kcov_remote_find(handle); > if (!remote) { > - spin_unlock_irqrestore(&kcov_remote_lock, flags); > + raw_spin_unlock_irqrestore(&kcov_remote_lock, flags); > return; > } > kcov_debug("handle = %llx, context: %s\n", handle, > @@ -869,7 +869,7 @@ void kcov_remote_start(u64 handle) > size = CONFIG_KCOV_IRQ_AREA_SIZE; > area = this_cpu_ptr(&kcov_percpu_data)->irq_area; > } > - spin_unlock_irqrestore(&kcov_remote_lock, flags); > + raw_spin_unlock_irqrestore(&kcov_remote_lock, flags); > > /* Can only happen when in_task(). */ > if (!area) { > @@ -1008,9 +1008,9 @@ void kcov_remote_stop(void) > spin_unlock(&kcov->lock); > > if (in_task()) { > - spin_lock(&kcov_remote_lock); > + raw_spin_lock(&kcov_remote_lock); > kcov_remote_area_put(area, size); > - spin_unlock(&kcov_remote_lock); > + raw_spin_unlock(&kcov_remote_lock); > } > > local_irq_restore(flags); > -- > 2.31.1 > > > > -- > The United States Coast Guard > Ruining Natural Selection since 1790 > > -- > You received this message because you are subscribed to the Google Groups "kasan-dev" group. > To unsubscribe from this group and stop receiving emails from it, send an email to kasan-dev+unsubscribe@...glegroups.com. > To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/20210809155909.333073de%40theseus.lan.
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