kern/118093: firewire bus reset hogs CPU, causing data to be lost

[Dieter]

The following reply was made to PR kern/118093; it has been noted by GNATS.

From: Dieter <freebsd at sopwith.solgatos.com>
To: freebsd-firewire at freebsd.org, bug-followup at freebsd.org
Cc:  
Subject: Re: kern/118093: firewire bus reset hogs CPU, causing data to be lost 
Date: Fri, 19 Dec 2008 11:02:21 +0000

 Here are the results of two more experiments:
 
 I tried to verify what spl the firewire code is at when calling
 printf(9) by adding the following block into fwohci.c just
 before one of the printfs.
 
 {
 #include <sys/types.h>
 #include <sys/systm.h>
   intrmask_t debug_spl;  /* __uint32_t */
   intrmask_t debug_spl_high;
   intrmask_t debug_spl_tty;
   intrmask_t debug_spl_fw;
   intrmask_t debug_spl_0;
   intrmask_t debug_spl_net;
 
   debug_spl = splhigh();
   debug_spl_high = spltty();
   debug_spl_tty = splfw();
   debug_spl_fw = splnet();
   debug_spl_net = splhigh();
   spl0();  /* void */
   debug_spl_0 = splhigh();
   splx(debug_spl);
 
   printf("fwohci_intr_core(): spl = 0x%x\n splhigh=0x%x spltty=0x%x splfw=0x%x splnet=0x%x spl0=0x%x\n",
          debug_spl, debug_spl_high, debug_spl_tty, debug_spl_fw, debug_spl_net, debug_spl_0);
 }
 
 But my results appear bogus:
 
 fwohci_intr_core(): spl = 0x0
  splhigh=0x0 spltty=0x0 splfw=0x0 splnet=0x0 spl0=0x0
 
 I have examined my code and the spl(9) man page several times
 but I can't find what is wrong.  Any clues?
 
 --------------------------------------------------------
 
 To isolate the effects of printf(9) from the firewire bus reset,
 I picked a trivial system call (chown(2)) and added some printf(9)
 calls.
 
 Calling chown several times and monitoring with systat -vmstat gives:
   1098 interrupts on the console IRQ
   93.1%Sys   6.7%Intr  0.2%User  0.0%Nice  0.0%Idle
 
 This did NOT interfere with Ethernet.
 
 So printf(9) interferes with Ethernet when called from the
 firewire driver, but not when called from a vanilla system call.
 
 --------------------------------------------------------
 
 sio0: <16550A-compatible COM port> port 0x3f8-0x3ff irq 4 flags 0x10 on acpi0
 sio0: type 16550A, console
 sio0: [FILTER]
 
 What does [FILTER] mean?  I don't see an explanation on the sio man page.