-----Original Message----- From: Dmitry Torokhov [mailto:dmitry.torokhov@gmail.com] Sent: Tuesday, January 5, 2021 12:01 PM To: Song Bao Hua (Barry Song) song.bao.hua@hisilicon.com Cc: tglx@linutronix.de; maz@kernel.org; gregkh@linuxfoundation.org; linux-input@vger.kernel.org; linux-kernel@vger.kernel.org; linuxarm@openeuler.org Subject: Re: [PATCH] genirq: add IRQF_NO_AUTOEN for request_irq
On Tue, Jan 05, 2021 at 11:26:12AM +1300, Barry Song wrote:
This patch originated from the discussion with Dmitry in the below thread:
https://lore.kernel.org/linux-input/20210102042902.41664-1-song.bao.hua@hi silicon.com/
there are many drivers which don't want interrupts enabled automatically due to request_irq(). So they are handling this issue by either way of the below two: (1) irq_set_status_flags(irq, IRQ_NOAUTOEN); request_irq(dev, irq...); (2) request_irq(dev, irq...); disable_irq(irq);
The code in the second way is silly and unsafe. In the small time gap between request_irq and disable_irq, interrupts can still come. The code in the first way is safe though we might be able to do it in the generic irq code.
I guess Dmitry also prefers genirq handles this as he said "What I would like to see is to allow passing something like IRQF_DISABLED to request_irq() so that we would not need neither irq_set_status_flags() nor disable_irq()" in the original email thread.
One of the reasons I dislike irq_set_status_flags() is that we have to call it before we actually granted our IRQ request...
If this one is accepted, hundreds of drivers with this problem will be handled afterwards.
Cc: Dmitry Torokhov dmitry.torokhov@gmail.com Signed-off-by: Barry Song song.bao.hua@hisilicon.com
include/linux/interrupt.h | 3 +++ kernel/irq/manage.c | 3 +++ kernel/irq/settings.h | 10 ++++++++++ 3 files changed, 16 insertions(+)
diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h index bb8ff9083e7d..0f22d277078c 100644 --- a/include/linux/interrupt.h +++ b/include/linux/interrupt.h @@ -61,6 +61,8 @@
interrupt handler after suspending interrupts. For systemwakeup devices users need to implement wakeup detection intheir interrupt handlers.
- IRQF_NO_AUTOEN - Don't enable IRQ automatically when users request it.
Users
*/
will enable it explicitly by enable_irq() later.#define IRQF_SHARED 0x00000080 #define IRQF_PROBE_SHARED 0x00000100 @@ -74,6 +76,7 @@ #define IRQF_NO_THREAD 0x00010000 #define IRQF_EARLY_RESUME 0x00020000 #define IRQF_COND_SUSPEND 0x00040000 +#define IRQF_NO_AUTOEN 0x00080000
#define IRQF_TIMER (__IRQF_TIMER | IRQF_NO_SUSPEND | IRQF_NO_THREAD)
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c index ab8567f32501..364e8b47d9ba 100644 --- a/kernel/irq/manage.c +++ b/kernel/irq/manage.c @@ -1693,6 +1693,9 @@ __setup_irq(unsigned int irq, struct irq_desc *desc,
struct irqaction *new)
irqd_set(&desc->irq_data, IRQD_NO_BALANCING); }
if (new->flags & IRQF_NO_AUTOEN)irq_settings_set_noautoen(desc);Can we make sure we refuse this request if the caller also specified IRQF_SHARED?
Right now, there is a warning for IRQF_SHARED + NOAUTOEN:
if (irq_settings_can_autoenable(desc)) { irq_startup(desc, IRQ_RESEND, IRQ_START_COND); } else { /* * Shared interrupts do not go well with disabling * auto enable. The sharing interrupt might request * it while it's still disabled and then wait for * interrupts forever. */ WARN_ON_ONCE(new->flags & IRQF_SHARED); /* Undo nested disables: */ desc->depth = 1; }
Of course, this could also be clearly rejected in the sanity-check of request_threaded_irq() if we want to totally prohibit this behavior:
int request_threaded_irq(unsigned int irq, irq_handler_t handler, irq_handler_t thread_fn, unsigned long irqflags, const char *devname, void *dev_id) { struct irqaction *action; struct irq_desc *desc; int retval;
if (irq == IRQ_NOTCONNECTED) return -ENOTCONN;
/* * Sanity-check: shared interrupts must pass in a real dev-ID, * otherwise we'll have trouble later trying to figure out * which interrupt is which (messes up the interrupt freeing * logic etc). * * Also IRQF_COND_SUSPEND only makes sense for shared interrupts and * it cannot be set along with IRQF_NO_SUSPEND. */ if (((irqflags & IRQF_SHARED) && !dev_id) || (!(irqflags & IRQF_SHARED) && (irqflags & IRQF_COND_SUSPEND)) || ((irqflags & IRQF_NO_SUSPEND) && (irqflags & IRQF_COND_SUSPEND))) return -EINVAL;
Thanks.
Thanks Barry