Re: [Linux-ia64] Help with Ingo scheduler on IA64

Nick Pollitt
2002-01-17T05:39:08Z

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With this hack, I'm getting an SMP boot all the way to the
init script 'Checking for new Hardware [OK]' before the
hang.

This patch is against linux+ia64+ingoJ0.

Nick

On Wed, Jan 16, 2002 at 05:42:30PM -0800, David Mosberger wrote:
> In case you're still fighting with Ingo's scheduler on 2.4.xx, you
> might want to try the attached patch. It's a gross hack to work
> around a race condition in set_cpus_allowed(). Without this hack, the
> kernel would almost always die as soon as it tried to migrate
> ksoftirqd_CPU1 from CPU 0 to CPU 1. With the patch, it boots up to
> the point where the serial line driver gets initialized, which is
> progress, I suppose.
>
> The fundamental problem is that current set_cpus_allowed() lets the
> same task run on two CPUs for a brief period of time. This violates
> scheduling assumptions made by the kernel and hence results in race
> conditions.
>
> --david

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diff -X /home/npollitt/dontdiff -Nur ingoj0.2/arch/ia64/kernel/process.c mylinux/arch/ia64/kernel/process.c
--- ingoj0.2/arch/ia64/kernel/process.c Wed Jan 16 21:32:45 2002
+++ mylinux/arch/ia64/kernel/process.c Wed Jan 16 19:43:00 2002
@@ -125,9 +125,6 @@
cpu_idle (void *unused)
{
/* endless idle loop with no priority at all */
- init_idle();
- current->nice = 20;
- current->counter = -100;

while (1) {
@@ -136,11 +133,10 @@
min_xtp();
#endif

- while (!current->need_resched) {
+ if (!current->need_resched) {
#ifdef CONFIG_IA64_SGI_SN
snidle();
#endif
- continue;
}

#ifdef CONFIG_IA64_SGI_SN
diff -X /home/npollitt/dontdiff -Nur ingoj0.2/arch/ia64/kernel/setup.c mylinux/arch/ia64/kernel/setup.c
--- ingoj0.2/arch/ia64/kernel/setup.c Wed Jan 16 21:32:45 2002
+++ mylinux/arch/ia64/kernel/setup.c Wed Jan 16 19:43:00 2002
@@ -375,10 +375,10 @@
{
#ifdef CONFIG_SMP
# define lpj c->loops_per_jiffy
-# define cpu c->processor
+# define cpum c->processor
#else
# define lpj loops_per_jiffy
-# define cpu 0
+# define cpum 0
#endif
char family[32], features[128], *cp;
struct cpuinfo_ia64 *c = v;
@@ -417,7 +417,7 @@
"cpu MHz : %lu.%06lu\n"
"itc MHz : %lu.%06lu\n"
"BogoMIPS : %lu.%02lu\n\n",
- cpu, c->vendor, family, c->model, c->revision, c->archrev,
+ cpum, c->vendor, family, c->model, c->revision, c->archrev,
features, c->ppn, c->number,
c->proc_freq / 1000000, c->proc_freq % 1000000,
c->itc_freq / 1000000, c->itc_freq % 1000000,
diff -X /home/npollitt/dontdiff -Nur ingoj0.2/arch/ia64/kernel/smp.c mylinux/arch/ia64/kernel/smp.c
--- ingoj0.2/arch/ia64/kernel/smp.c Fri Dec 21 09:41:53 2001
+++ mylinux/arch/ia64/kernel/smp.c Wed Jan 16 21:21:19 2002
@@ -186,6 +186,29 @@
}

void
+smp_send_reschedule_all(void)
+{
+ send_IPI_all(IA64_IPI_RESCHEDULE);
+}
+
+static spinlock_t migration_lock = SPIN_LOCK_UNLOCKED;
+static task_t *new_task;
+
+/*
+ * This function sends a 'task migration' IPI to another CPU.
+ * Must be called from syscall contexts, with interrupts *enabled*.
+ */
+void smp_migrate_task(int cpu, task_t *p)
+{
+ /*
+ * The target CPU will unlock the migration spinlock:
+ */
+ spin_lock(&migration_lock);
+ new_task = p;
+ smp_send_reschedule(cpu);
+}
+
+void
smp_flush_tlb_all (void)
{
smp_call_function ((void (*)(void *))__flush_tlb_all,0,1,1);
diff -X /home/npollitt/dontdiff -Nur ingoj0.2/arch/ia64/kernel/smpboot.c mylinux/arch/ia64/kernel/smpboot.c
--- ingoj0.2/arch/ia64/kernel/smpboot.c Wed Jan 16 21:32:45 2002
+++ mylinux/arch/ia64/kernel/smpboot.c Wed Jan 16 19:43:00 2002
@@ -323,7 +323,7 @@
extern void perfmon_init_percpu(void);
#endif

- cpuid = smp_processor_id();
+ cpuid = cpu();
phys_id = hard_smp_processor_id();

if (test_and_set_bit(cpuid, &cpu_online_map)) {
@@ -380,6 +380,7 @@
while (!atomic_read(&smp_commenced))
;

+ init_idle();
Dprintk("CPU %d is starting idle.\n", smp_processor_id());
return cpu_idle();
}
@@ -416,11 +417,10 @@
if (!idle)
panic("No idle process for CPU %d", cpu);

- task_set_cpu(idle, cpu); /* we schedule the first task manually */
+ idle->cpu = cpu;

ia64_cpu_to_sapicid[cpu] = sapicid;

- del_from_runqueue(idle);
unhash_process(idle);
init_tasks[cpu] = idle;

@@ -481,8 +481,7 @@
printk("Boot processor id 0x%x/0x%x\n", 0, boot_cpu_id);

global_irq_holder = 0;
- current->processor = 0;
- init_idle();
+ current->cpu = 0;

/*
* If SMP should be disabled, then really disable it!
diff -X /home/npollitt/dontdiff -Nur ingoj0.2/arch/ia64/mm/fault.c mylinux/arch/ia64/mm/fault.c
--- ingoj0.2/arch/ia64/mm/fault.c Fri Nov 9 14:26:17 2001
+++ mylinux/arch/ia64/mm/fault.c Wed Jan 16 19:43:00 2002
@@ -194,8 +194,7 @@
out_of_memory:
up_read(&mm->mmap_sem);
if (current->pid == 1) {
- current->policy |= SCHED_YIELD;
- schedule();
+ yield();
down_read(&mm->mmap_sem);
goto survive;
}
diff -X /home/npollitt/dontdiff -Nur ingoj0.2/arch/ia64/tools/print_offsets.c mylinux/arch/ia64/tools/print_offsets.c
--- ingoj0.2/arch/ia64/tools/print_offsets.c Fri Nov 9 14:26:17 2001
+++ mylinux/arch/ia64/tools/print_offsets.c Wed Jan 16 19:43:00 2002
@@ -54,7 +54,7 @@
{ "IA64_TASK_PTRACE_OFFSET", offsetof (struct task_struct, ptrace) },
{ "IA64_TASK_SIGPENDING_OFFSET", offsetof (struct task_struct, sigpending) },
{ "IA64_TASK_NEED_RESCHED_OFFSET", offsetof (struct task_struct, need_resched) },
- { "IA64_TASK_PROCESSOR_OFFSET", offsetof (struct task_struct, processor) },
+ { "IA64_TASK_PROCESSOR_OFFSET", offsetof (struct task_struct, cpu) },
{ "IA64_TASK_THREAD_OFFSET", offsetof (struct task_struct, thread) },
{ "IA64_TASK_THREAD_KSP_OFFSET", offsetof (struct task_struct, thread.ksp) },
#ifdef CONFIG_PERFMON
diff -X /home/npollitt/dontdiff -Nur ingoj0.2/include/asm-ia64/bitops.h mylinux/include/asm-ia64/bitops.h
--- ingoj0.2/include/asm-ia64/bitops.h Wed Jan 16 21:32:46 2002
+++ mylinux/include/asm-ia64/bitops.h Wed Jan 16 19:43:37 2002
@@ -368,6 +368,7 @@

#ifdef __KERNEL__

+#define __clear_bit(nr, addr) clear_bit(nr, addr)
#define ext2_set_bit test_and_set_bit
#define ext2_clear_bit test_and_clear_bit
#define ext2_test_bit test_bit
diff -X /home/npollitt/dontdiff -Nur ingoj0.2/include/asm-ia64/mmu_context.h mylinux/include/asm-ia64/mmu_context.h
--- ingoj0.2/include/asm-ia64/mmu_context.h Fri Nov 9 14:26:17 2001
+++ mylinux/include/asm-ia64/mmu_context.h Wed Jan 16 21:12:16 2002
@@ -118,6 +118,27 @@
reload_context(next);
}

+/*
+ * Every architecture must define this function. It's the fastest
+ * way of searching a 168-bit bitmap where the first 128 bits are
+ * unlikely to be set. It's guaranteed that at least one of the 168
+ * bits is cleared.
+ */
+#if MAX_RT_PRIO != 128 || MAX_PRIO != 173
+/* # error update this function. */
+#endif
+
+static inline int sched_find_first_zero_bit(unsigned long *b)
+{
+ unsigned long rt;
+
+ rt = b[0] & b[1];
+ if (unlikely(rt != 0xffffffffffffffff))
+ return find_first_zero_bit(b, MAX_RT_PRIO);
+
+ return ffz(b[2]) + MAX_RT_PRIO;
+}
+
#define switch_mm(prev_mm,next_mm,next_task,cpu) activate_mm(prev_mm, next_mm)

# endif /* ! __ASSEMBLY__ */
diff -X /home/npollitt/dontdiff -Nur ingoj0.2/include/asm-ia64/smp.h mylinux/include/asm-ia64/smp.h
--- ingoj0.2/include/asm-ia64/smp.h Fri Nov 9 14:26:17 2001
+++ mylinux/include/asm-ia64/smp.h Wed Jan 16 21:00:07 2002
@@ -27,7 +27,7 @@
#define SMP_IRQ_REDIRECTION (1 << 0)
#define SMP_IPI_REDIRECTION (1 << 1)

-#define smp_processor_id() (current->processor)
+#define smp_processor_id() (current->cpu)

extern struct smp_boot_data {
int cpu_count;
@@ -48,6 +48,9 @@

extern unsigned long ap_wakeup_vector;

+extern void smp_send_reschedule(int cpu);
+extern void smp_send_reschedule_all(void);
+
/*
* Function to map hard smp processor id to logical id. Slow, so
* don't use this in performance-critical code.
@@ -109,12 +112,6 @@
}

#define NO_PROC_ID 0xffffffff /* no processor magic marker */
-
-/*
- * Extra overhead to move a task from one cpu to another (due to TLB and cache misses).
- * Expressed in "negative nice value" units (larger number means higher priority/penalty).
- */
-#define PROC_CHANGE_PENALTY 20

extern void __init init_smp_config (void);
extern void smp_do_timer (struct pt_regs *regs);
diff -X /home/npollitt/dontdiff -Nur ingoj0.2/include/linux/smp.h mylinux/include/linux/smp.h
--- ingoj0.2/include/linux/smp.h Wed Jan 16 21:32:55 2002
+++ mylinux/include/linux/smp.h Wed Jan 16 21:05:20 2002
@@ -24,12 +24,6 @@
extern void smp_send_stop(void);

/*
- * sends a 'reschedule' event to another CPU:
- */
-extern void FASTCALL(smp_send_reschedule(int cpu));
-
-
-/*
* Boot processor call to load the other CPU's
*/
extern void smp_boot_cpus(void);
diff -X /home/npollitt/dontdiff -Nur ingoj0.2/kernel/printk.c mylinux/kernel/printk.c
--- ingoj0.2/kernel/printk.c Wed Jan 16 21:32:55 2002
+++ mylinux/kernel/printk.c Wed Jan 16 19:43:02 2002
@@ -25,6 +25,8 @@
#include <linux/init.h>
#include <linux/module.h>
#include <linux/interrupt.h> /* For in_interrupt() */
+#include <linux/config.h>
+#include <linux/delay.h>

#include <asm/uaccess.h>

diff -X /home/npollitt/dontdiff -Nur ingoj0.2/kernel/sched.c mylinux/kernel/sched.c
--- ingoj0.2/kernel/sched.c Wed Jan 16 21:32:55 2002
+++ mylinux/kernel/sched.c Wed Jan 16 20:48:06 2002
@@ -94,6 +94,8 @@
p->array = array;
}

+struct task_struct * init_tasks[NR_CPUS] __initdata = {&init_task, };
+
/*
* A task is 'heavily interactive' if it has reached the
* bottom 25% of the SCHED_OTHER priority range - in this
@@ -275,7 +277,7 @@
spin_unlock_irq(&this_rq()->lock);
}

-static inline void context_switch(task_t *prev, task_t *next)
+static inline void context_switch(task_t *prev, task_t *next, int dont_clear)
{
struct mm_struct *mm = next->mm;
struct mm_struct *oldmm = prev->active_mm;
@@ -290,7 +292,8 @@
switch_mm(oldmm, mm, next, smp_processor_id());

if (!prev->mm) {
- prev->active_mm = NULL;
+ if (!dont_clear)
+ prev->active_mm = NULL;
mmdrop(oldmm);
}

@@ -614,7 +617,7 @@
if (likely(prev != next)) {
rq->nr_switches++;
rq->curr = next;
- context_switch(prev, next);
+ context_switch(prev, next, 0);
/*
* The runqueue pointer might be from another CPU
* if the new task was last running on a different
diff -X /home/npollitt/dontdiff -Nur ingoj0.2/kernel/timer.c mylinux/kernel/timer.c
--- ingoj0.2/kernel/timer.c Wed Jan 16 21:32:55 2002
+++ mylinux/kernel/timer.c Wed Jan 16 20:42:10 2002
@@ -585,17 +585,16 @@

update_one_process(p, user_tick, system, cpu);
if (p->pid) {
- if (--p->counter <= 0) {
- p->counter = 0;
- p->need_resched = 1;
- }
- if (p->nice > 0)
+ if (p->__nice > 0)
kstat.per_cpu_nice[cpu] += user_tick;
else
kstat.per_cpu_user[cpu] += user_tick;
kstat.per_cpu_system[cpu] += system;
- } else if (really_local_bh_count() || really_local_irq_count() > 1)
- kstat.per_cpu_system[cpu] += system;
+ } else {
+ if (really_local_bh_count() || really_local_irq_count() > 1)
+ kstat.per_cpu_system[cpu] += system;
+ }
+ sched_tick(p);
}

/*