Messages in this thread Patch in this message | | | Date | Tue, 18 Dec 2007 16:23:11 +0100 | From | "Remy Bohmer" <> | Subject | Re: [PATCH] atmel_serial: Split the interrupt handler |
| |
Hello Haavard,
A few remarks:
> From: Remy Bohmer <hskinnemoen@atmel.com>
My name, at your address ;-)))
> This patch splits up the interrupt handler of the serial port > into a interrupt top-half and a tasklet.
I see you moved the handling of the sysrq-key to the tasklet. This was actually a very nice feature in the IRQ-top half on preempt-RT. This helps debugging running away RT-processes.
> In this version of the patch, we try to only do things that are > absolutely necessary in the interrupt handler, storing away the > status register along with the received character and letting the > tasklet handle break, sysrq, error flags, etc.
Preempt-RT now absolutely requires my (4th) IRQ_NODELAY patch, because the spinlock now is always inside the code, and not only in theexception path, and thus without my NO_DELAY patch we have a panic during boot. On preempt-RT this spinlock must be a raw-spinlock. (If this type is known in the mainline kernel, you can apply that patch it anyway)
BTW: Attached I have added a 2nd patch that I use for Preempt-RT. (For cleaner startup, and to get rid of useless IRQ-threads.
> This patch should apply on top of the cleanup patch I sent earlier
For the cleanup patch: Acked-by: Remy Bohmer <linux@bohmer.net>
> today. Or at least I think so...I'll send the full series once > everyone are happy.
So, for this patch: I am almost happy ;-)
Kind Regards,
Remy This patch prevents starting up a useless IRQ-thread for IRQ-1, because this IRQ is running in IRQF_NODELAY context due to the timer interrupt.
Signed-off-by: Remy Bohmer <linux@bohmer.net> --- drivers/serial/atmel_serial.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)
Index: linux-2.6.23/drivers/serial/atmel_serial.c =================================================================== --- linux-2.6.23.orig/drivers/serial/atmel_serial.c 2007-12-18 15:49:02.000000000 +0100 +++ linux-2.6.23/drivers/serial/atmel_serial.c 2007-12-18 15:56:37.000000000 +0100 @@ -549,6 +549,7 @@ static int atmel_startup(struct uart_por { struct atmel_uart_port *atmel_port = (struct atmel_uart_port *) port; int retval; + unsigned long irqflags = IRQF_SHARED; /* * Ensure that no interrupts are enabled otherwise when @@ -557,10 +558,17 @@ static int atmel_startup(struct uart_por */ UART_PUT_IDR(port, -1); +#ifdef CONFIG_PREEMPT_RT + /* IRQ1 is the System IRQ, which is shared with the Timer-IRQ, and + thus it is running in IRQF_NODELAY context. By setting this flag + here also, we prevent starting up a useless IRQ-thread.*/ + if (port->irq == 1) + irqflags |= IRQF_NODELAY; +#endif /* * Allocate the IRQ */ - retval = request_irq(port->irq, atmel_interrupt, IRQF_SHARED, + retval = request_irq(port->irq, atmel_interrupt, irqflags, "atmel_serial", port); if (retval) { printk("atmel_serial: atmel_startup - Can't get irq\n"); | |