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Date: Tue, 18 Mar 2003 15:25:24 +0100
From: Maarten Ghijsen <maarten.ghijsen@planet.nl>
Subject: system hangs on wake_up call from IRQ handler
To: linux-kernel@vger.kernel.org
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Hello,

I am busy on writing a driver for a PCI Card. Amongst others my driver
includes an IOCTL command for starting a DMA transfer (user-->PCI card or
PCI card-->user). In my handler for this command I instruct the PciCard to
start a DMA transfer and than wait (sleep) for the DMA to complete. I wait
using the wait_event function, which waits for an event that is 'fired'
(wake_up) from the DMA done interrupt handler. As soon as I make the call to
wake_up, from the DMA done interrupt handler, my system hangs completely. 

Does anyone have any idea why the system hangs on the wake-up from the
interrupt handler?

Below you will find some pseudo code for with the wait_event and the
wake_up:

// wait from DMA IOCTL handler
void Dta1xxTxIoCtlDma()
{
	startdma();

	wait_event(my_wait_queue, ( 1==dma_done_flag) );

	return;
}

// wake_up from interrupt handler
void Dta1xxIRQ()
{
	if ( IsDmaDoneInterruptSet() ) {
		dma_done_flag = 1;
		wake_up(&my_wait_queue);
	}
}

I am using linux kernel version 2.4.18.

Regards,
 
Maarten