Hi Tom,
the problem occurs even if i set enable_llm=0. The while loop is now not
touched and the rpi deadlocks too.
As far as i understand it, the sdhci.c is the base for all sdhci card
readers and the sdhci-*.c implement the ops for the specific hardware.
My problem is, that i dont have an other sdhci card reader here. It wont
be possible to boot from, but i could try to read from it on a rt
kernel. If i compile the sdhci_bcm2708 as a module, i could not get a
device info from the rpi reader. Maybe an other reader works, then the
real problem sits in sdhci_bcm2708.c (or at bad luck, it shows an bigger
problem in sdhci.c).
Georg
Am 29.06.2013 23:36, schrieb Tom Cook:
This is as far as I've got too. I think you need to make the while loop
conditional on CONFIG_PREEMPT_RT_FULL but I haven't had a chance to try it.
Tom
On 29 Jun 2013 21:16, "Georg Gast" <georg@xxxxxxxxxxxxxxxx
<mailto:georg@xxxxxxxxxxxxxxxx>> wrote:
Hi there!
Currently i try to locate a bug in drivers/mmc/host/sdhci.c on
RaspberryPi. I know it is not the mainline kernel...
Currently i use Kernel 3.8.13 and RT Patch 3.8.13-rt12 on the kernel
found at git://github.com/raspberrypi/__linux.git
<http://github.com/raspberrypi/linux.git> on branch rpi-3.8.y.
The bug shows up at booting and after 3 seconds of booting as it
wants to mount the rootfs in a deadlock. as i compiled sdhci_bcm2708
as a module i can boot the kernel and system as i pushed the system
to a usb stick. As far as good.
Now i try to find the bug, if the rootfs is on the sdcard. I narrowd
the deadlock down to the following lines:
void sdhci_spin_lock_irqsave(struct sdhci_host *host,unsigned long
*flags)
{
return;
#ifdef CONFIG_PREEMPT
if(enable_llm)
{
while(sdhci_locked)
{
preempt_schedule();
}
spin_lock_irqsave(&host->lock,__*flags);
disable_irq(host->irq);
if(host->second_irq)
disable_irq(host->second_irq);
local_irq_enable();
}
else
#endif
spin_lock_irqsave(&host->lock,__*flags);
}
void sdhci_spin_unlock_irqrestore(__struct sdhci_host *host,unsigned
long flags)
{
return;
#ifdef CONFIG_PREEMPT
if(enable_llm)
{
local_irq_disable();
if(host->second_irq)
enable_irq(host->second_irq);
enable_irq(host->irq);
}
#endif
spin_unlock_irqrestore(&host->__lock,flags);
}
in drivers/mmc/host/sdhci.c . The both return statements are added
by me. Now i can boot the RT Preempt kernel but it is for sure not
the right fix.
My problem is, that i dont know how those both functions should work
with the rt preempt patch.
What can you suggest me to fix that deadlock? I already bought the
book "Linux Kernel Development" but i dont know how the kernel works
exaktly with the PREEMPT patch. Can you point me to a site which
shows how RTPREEMPT works in the irqsave/restore functions or can
you please describe it to me?
Thank you
Georg
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