Is the preemptive kernel patch unsafe for 8xx/PPC?
ebs at innocent.com
Fri Dec 13 17:09:48 EST 2002
At 12:35 PM 12/12/2002, you wrote:
>Was that the 2.4.19-2 patch? What were the bugs and have you fixed them?
I had the following issues with 2.4.19-2 (2.4.20-1 is identical in this
diff -urN linux-2.4.20/arch/ppc/kernel/entry.S linux/arch/ppc/kernel/entry.S
--- linux-2.4.20/arch/ppc/kernel/entry.S 2002-11-28
+++ linux/arch/ppc/kernel/entry.S 2002-12-11 02:34:47.000000000 -0500
@@ -278,6 +278,41 @@
+ lwz r3,PREEMPT_COUNT(r2)
+ cmpi 0,r3,1
+ bge ret_from_except
+ lwz r5,_MSR(r1)
+ andi. r5,r5,MSR_PR
+ bne do_signal_ret
<rest of the diff is skipped>
I had to change the last command to "bne ret_from_except".
I checked MontaVista tree, and they have "ret_from_except" there also.
Without this change trivial code:
while (true) ;
locked the box completely.
2) include/asm-ppc/pgalloc.h There are curly brackets missing in
3) to support 440GP you have to modify arc/ppc/kernel/irc.c:preempt_intercept:
#if !defined(CONFIG_4xx) || defined(CONFIG_440)
With these changes (an maybe some others I forgot to mention here :),
I have pretty stable preemptable kernel (2.4.19, PPC440GP & 405GP, also
with rtsched patch by George Anzinger)
Eugene Surovegin <mailto:ebs at innocent.com>
** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/
More information about the Linuxppc-dev