On 13 May 2002, Frederic Roussel wrote:
> Package: gcc-2.95
> Version: 1:2.95.4-9
> Severity: normal
>
> -- System Information
> Debian Release: 3.0
> Kernel Version: Linux big2 2.4.19-pre8-30 #1 SMP Mon May 13 18:01:01 PDT
> 2002 alpha unknown
>
> Versions of the packages gcc-2.95 depends on:
> ii binutils 2.12.90.0.1-5 The GNU assembler, linker and binary
> utiliti
> ii cpp-2.95 2.95.4-9 The GNU C preprocessor.
> ii gcc 2.95.4-14 The GNU C compiler.
> ii libc6.1 2.2.5-6 GNU C Library: Shared libraries and
> Timezone
>
> If I compile a kernel 2.4.x (I tried with x >= 17) on a Compaq DS20, the
> newly compiled kernel oopses in the fontion:
> smp_tune_scheduling defined in file arch/alpha/kernel/smp.c
>
> The `switch' statement in that function is where the Oops happens, at
> least I believe so: as an experiment I've hard-coded the `on_chip_cache'
> variable and commented out the whole switch, the kernel booted up fine.
>
> I compiled with gcc-3.0.4 and the problem disappeared.
Try the patch below to see if it fixes things. There is a code generation
problem in 2.95.4, but it's mostly irrelevent since the kernel code that's
being miscompiled doesn't even need to be used in the 2.4 kernels. I
tried submitting this patch to upstream kernel folks, but it got ignored
several times and I didn't have the time to follow up further.
C
Index: arch/alpha/kernel/smp.c
===================================================================
RCS file: /home/cvs/linux-24/arch/alpha/kernel/smp.c,v
retrieving revision 1.1.1.4
retrieving revision 1.4
diff -u -r1.1.1.4 -r1.4
--- arch/alpha/kernel/smp.c 11 Oct 2001 15:41:35 -0000 1.1.1.4
+++ arch/alpha/kernel/smp.c 11 Oct 2001 15:51:36 -0000 1.4
@@ -80,7 +80,6 @@
int smp_num_probed; /* Internal processor count */
int smp_num_cpus = 1; /* Number that came online. */
int smp_threads_ready; /* True once the per process idle is forked. */
-cycles_t cacheflush_time;
int __cpu_number_map[NR_CPUS];
int __cpu_logical_map[NR_CPUS];
@@ -212,63 +211,6 @@
/*
- * Rough estimation for SMP scheduling, this is the number of cycles it
- * takes for a fully memory-limited process to flush the SMP-local cache.
- *
- * We are not told how much cache there is, so we have to guess.
- */
-static void __init
-smp_tune_scheduling (int cpuid)
-{
- struct percpu_struct *cpu;
- unsigned long on_chip_cache;
- unsigned long freq;
-
- cpu = (struct percpu_struct*)((char*)hwrpb + hwrpb->processor_offset
- + cpuid * hwrpb->processor_size);
- switch (cpu->type)
- {
- case EV45_CPU:
- on_chip_cache = 16 + 16;
- break;
-
- case EV5_CPU:
- case EV56_CPU:
- on_chip_cache = 8 + 8 + 96;
- break;
-
- case PCA56_CPU:
- on_chip_cache = 16 + 8;
- break;
-
- case EV6_CPU:
- case EV67_CPU:
- on_chip_cache = 64 + 64;
- break;
-
- default:
- on_chip_cache = 8 + 8;
- break;
- }
-
- freq = hwrpb->cycle_freq ? : est_cycle_freq;
-
-#if 0
- /* Magic estimation stolen from x86 port. */
- cacheflush_time = freq / 1024L * on_chip_cache / 5000L;
-
- printk("Using heuristic of %d cycles.\n",
- cacheflush_time);
-#else
- /* Magic value to force potential preemption of other CPUs. */
- cacheflush_time = INT_MAX;
-
- printk("Using heuristic of %d cycles.\n",
- cacheflush_time);
-#endif
-}
-
-/*
* Send a message to a secondary's console. "START" is one such
* interesting message. ;-)
*/
@@ -607,7 +549,6 @@
current->processor = boot_cpuid;
smp_store_cpu_info(boot_cpuid);
- smp_tune_scheduling(boot_cpuid);
smp_setup_percpu_timer(boot_cpuid);
init_idle();
--
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