Messages in this thread | | | Subject | Re: [PATCH] tty/sysrq: Convert show_lock to raw_spinlock_t | From | Julien Grall <> | Date | Mon, 4 Mar 2019 17:21:57 +0000 |
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(CC correctly linux-rt-users)
On 04/03/2019 17:20, Julien Grall wrote: > At the moment show_lock is implemented using spin_lock_t and called from > an interrupt context on Arm64. The following backtrace was triggered by: > > 42sh# echo l > /proc/sysrq-trigger > > [ 4432.073756] sysrq: SysRq : Show backtrace of all active CPUs > [ 4432.403422] BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:974 > [ 4432.403424] sysrq: CPU6: > [ 4432.403426] in_atomic(): 1, irqs_disabled(): 128, pid: 2410, name: kworker/u16:2 > > [...] > > [ 4432.403581] Call trace: > [ 4432.403584] dump_backtrace+0x0/0x148 > [ 4432.403586] show_stack+0x14/0x20 > [ 4432.403588] dump_stack+0x9c/0xd4 > [ 4432.403592] ___might_sleep+0x1cc/0x298 > [ 4432.403595] rt_spin_lock+0x5c/0x70 > [ 4432.403596] showacpu+0x34/0x68 > [ 4432.403599] flush_smp_call_function_queue+0xd4/0x278 > [ 4432.403602] generic_smp_call_function_single_interrupt+0x10/0x18 > [ 4432.403605] handle_IPI+0x26c/0x668 > [ 4432.403607] gic_handle_irq+0x9c/0xa0 > [ 4432.403609] el1_irq+0xb4/0x13c > > With RT-patches, spin_lock can now sleep and therefore cannot be used from > interrupt context. Use a raw_spin_lock instead to prevent the lock to > sleep. > > Signed-off-by: Julien Grall <julien.grall@arm.com> > --- > drivers/tty/sysrq.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c > index 1f03078ec352..8473557c7ab2 100644 > --- a/drivers/tty/sysrq.c > +++ b/drivers/tty/sysrq.c > @@ -208,7 +208,7 @@ static struct sysrq_key_op sysrq_showlocks_op = { > #endif > > #ifdef CONFIG_SMP > -static DEFINE_SPINLOCK(show_lock); > +static DEFINE_RAW_SPINLOCK(show_lock); > > static void showacpu(void *dummy) > { > @@ -218,10 +218,10 @@ static void showacpu(void *dummy) > if (idle_cpu(smp_processor_id())) > return; > > - spin_lock_irqsave(&show_lock, flags); > + raw_spin_lock_irqsave(&show_lock, flags); > pr_info("CPU%d:\n", smp_processor_id()); > show_stack(NULL, NULL); > - spin_unlock_irqrestore(&show_lock, flags); > + raw_spin_unlock_irqrestore(&show_lock, flags); > } > > static void sysrq_showregs_othercpus(struct work_struct *dummy) >
-- Julien Grall
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