On Wed, 3 Jun 2009, Andrew Morton wrote:
(switched to email. Please respond via emailed reply-to-all, not via the
bugzilla web interface).
On Wed, 3 Jun 2009 16:45:33 GMT
bugzilla-daemon@xxxxxxxxxxxxxxxxxxx wrote:
http://bugzilla.kernel.org/show_bug.cgi?id=13444
Summary: SparcServer 1000E SMP can cause kernel-nullpointer
with some hw configurations
Product: Platform Specific/Hardware
Version: 2.5
Kernel Version: 2.4.37
Platform: All
OS/Version: Linux
Tree: Mainline
Status: NEW
Severity: normal
Priority: P1
Component: SPARC32
AssignedTo: zaitcev@xxxxxxxxx
ReportedBy: oftedal@xxxxxxxxx
Regression: No
Created an attachment (id=21732)
--> (http://bugzilla.kernel.org/attachment.cgi?id=21732)
SUN4D-SMP mode patch
SparcServer 1000E/SUN4D machines will cause a kernel-nullpointer when running
in SMP-mode with certain hw configurations.
According to Sun documentation Slot A on the systemboards should be filled with
cpu modules first. This will fill physical cpu-slots 0,2,4,8 with cpus first.
The current smp code will then fill the init_tasks-array using the physical
cpu-mapping.
The scheduler on the other hand uses the logical cpu-mapping.
So in a two cpu system with two systemboards cpu-slots 0 and 2 will be occupied
and init_tasks-array position 0 and 2 will contain a idle_task. But the
scheduler will access init_tasks position 0 and 1 which will cause an error.
Any sparcserver 1000(E) system with 2 systemboards and 2 cpus, with 1 cpu per
board will cause this error.
Thanks, but handling patches via bugzilla is far from preferred.
Please send the patch via email, as a reply-to-all to this email. The
patch should include a full description and a Signed-off-by:, as per
Documentation/SubmittingPatches.
As mentioned in the bug-report(#13444) the sun4d-SMP code on
2.4-series kernels(2.4.37) uses the physical cpu-mapping when inserting
tasks into the init_tasks array.
And the scheduler uses the logical cpu-mapping which will cause a
kernel nullpointer when there are gaps in the physical cpu-mapping.
The attached patch uses the cpucount variable, which can be used to find
the next logical slot in the init_tasks array. As it is only incremented
when a cpu is successfully started.
(I hope this was more compliant with kernel-bugfixing standards. I am new
to this)
Signed-off-by: Kjetil Oftedal <oftedal@xxxxxxxxx>
---
diff --git a/arch/sparc/kernel/sun4d_smp.c b/arch/sparc/kernel/sun4d_smp.c
index 9bb7f78..5b9b34e 100644
--- a/arch/sparc/kernel/sun4d_smp.c
+++ b/arch/sparc/kernel/sun4d_smp.c
@@ -221,7 +221,9 @@ void __init smp4d_boot_cpus(void)
cpucount++;
p = init_task.prev_task;
- init_tasks[i] = p;
+
+ /* The scheduler uses the logical cpu mapping when accessing this array */
+ init_tasks[cpucount] = p;
p->processor = i;
p->cpus_runnable = 1 << i; /* we schedule the first task manually */
--
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