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Subject[PATCH] 2.4: preempt-kernel for MIPS
From
Date
MontaVista has provided the community with MIPS architecture support for
the preemptive kernel patch. Thanks specifically to Jun Sun of
MontaVista for the work.

This patch will be integrated with the base 2.4 preempt-kernel patch
soon. For now, this is diffed on _top_ of preempt-kernel for
2.4.19-pre8. While it is against 2.4.19-pre8, it should hopefully also
apply to a recent MIPS tree checkout.

Comments are welcome. Enjoy,

Robert Love





diff -urN linux-2.4.19-pre8-preempt/arch/mips/config.in linux/arch/mips/config.in
--- linux-2.4.19-pre8-preempt/arch/mips/config.in Wed May 8 15:09:53 2002
+++ linux/arch/mips/config.in Wed May 8 15:54:35 2002
@@ -468,6 +468,7 @@
# bool ' Access.Bus support' CONFIG_ACCESSBUS
# fi
fi
+dep_bool 'Preemptible Kernel' CONFIG_PREEMPT $CONFIG_NEW_IRQ
endmenu

if [ "$CONFIG_ISA" = "y" ]; then
diff -urN linux-2.4.19-pre8-preempt/arch/mips/kernel/i8259.c linux/arch/mips/kernel/i8259.c
--- linux-2.4.19-pre8-preempt/arch/mips/kernel/i8259.c Wed May 8 15:09:53 2002
+++ linux/arch/mips/kernel/i8259.c Wed May 8 15:54:35 2002
@@ -8,6 +8,7 @@
* Copyright (C) 1992 Linus Torvalds
* Copyright (C) 1994 - 2000 Ralf Baechle
*/
+#include <linux/sched.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/ioport.h>
diff -urN linux-2.4.19-pre8-preempt/arch/mips/kernel/irq.c linux/arch/mips/kernel/irq.c
--- linux-2.4.19-pre8-preempt/arch/mips/kernel/irq.c Wed May 8 15:09:53 2002
+++ linux/arch/mips/kernel/irq.c Wed May 8 15:56:16 2002
@@ -8,6 +8,8 @@
* Copyright (C) 1992 Linus Torvalds
* Copyright (C) 1994 - 2000 Ralf Baechle
*/
+
+#include <linux/sched.h>
#include <linux/config.h>
#include <linux/kernel.h>
#include <linux/delay.h>
@@ -19,11 +21,13 @@
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/random.h>
-#include <linux/sched.h>
+#include <linux/spinlock.h>
+#include <linux/ptrace.h>

#include <asm/atomic.h>
#include <asm/system.h>
#include <asm/uaccess.h>
+#include <asm/debug.h>

/*
* Controller mappings for all interrupt sources:
@@ -420,6 +424,8 @@
struct irqaction * action;
unsigned int status;

+ preempt_disable();
+
kstat.irqs[cpu][irq]++;
spin_lock(&desc->lock);
desc->handler->ack(irq);
@@ -481,6 +487,27 @@

if (softirq_pending(cpu))
do_softirq();
+
+#if defined(CONFIG_PREEMPT)
+ while (--current->preempt_count == 0) {
+ db_assert(intr_off());
+ db_assert(!in_interrupt());
+
+ if (current->need_resched == 0) {
+ break;
+ }
+
+ current->preempt_count ++;
+ sti();
+ if (user_mode(regs)) {
+ schedule();
+ } else {
+ preempt_schedule();
+ }
+ cli();
+ }
+#endif
+
return 1;
}

diff -urN linux-2.4.19-pre8-preempt/arch/mips/mm/extable.c linux/arch/mips/mm/extable.c
--- linux-2.4.19-pre8-preempt/arch/mips/mm/extable.c Wed May 8 15:09:53 2002
+++ linux/arch/mips/mm/extable.c Wed May 8 15:54:35 2002
@@ -3,6 +3,7 @@
*/
#include <linux/config.h>
#include <linux/module.h>
+#include <linux/sched.h>
#include <linux/spinlock.h>
#include <asm/uaccess.h>

diff -urN linux-2.4.19-pre8-preempt/include/asm-mips/smplock.h linux/include/asm-mips/smplock.h
--- linux-2.4.19-pre8-preempt/include/asm-mips/smplock.h Wed May 8 15:09:11 2002
+++ linux/include/asm-mips/smplock.h Wed May 8 15:57:41 2002
@@ -5,12 +5,21 @@
*
* Default SMP lock implementation
*/
+#include <linux/config.h>
#include <linux/interrupt.h>
#include <linux/spinlock.h>

extern spinlock_t kernel_flag;

+#ifdef CONFIG_SMP
#define kernel_locked() spin_is_locked(&kernel_flag)
+#else
+#ifdef CONFIG_PREEMPT
+#define kernel_locked() preempt_get_count()
+#else
+#define kernel_locked() 1
+#endif
+#endif

/*
* Release global kernel lock and global interrupt lock
@@ -42,8 +51,14 @@
*/
extern __inline__ void lock_kernel(void)
{
+#ifdef CONFIG_PREEMPT
+ if (current->lock_depth == -1)
+ spin_lock(&kernel_flag);
+ ++current->lock_depth;
+#else
if (!++current->lock_depth)
spin_lock(&kernel_flag);
+#endif
}

extern __inline__ void unlock_kernel(void)
diff -urN linux-2.4.19-pre8-preempt/include/asm-mips/softirq.h linux/include/asm-mips/softirq.h
--- linux-2.4.19-pre8-preempt/include/asm-mips/softirq.h Wed May 8 15:09:11 2002
+++ linux/include/asm-mips/softirq.h Wed May 8 15:54:35 2002
@@ -15,6 +15,7 @@

static inline void cpu_bh_disable(int cpu)
{
+ preempt_disable();
local_bh_count(cpu)++;
barrier();
}
@@ -23,6 +24,7 @@
{
barrier();
local_bh_count(cpu)--;
+ preempt_enable();
}


@@ -36,6 +38,7 @@
cpu = smp_processor_id(); \
if (!--local_bh_count(cpu) && softirq_pending(cpu)) \
do_softirq(); \
+ preempt_enable(); \
} while (0)

#define in_softirq() (local_bh_count(smp_processor_id()) != 0)
diff -urN linux-2.4.19-pre8-preempt/include/asm-mips/system.h linux/include/asm-mips/system.h
--- linux-2.4.19-pre8-preempt/include/asm-mips/system.h Wed May 8 15:09:11 2002
+++ linux/include/asm-mips/system.h Wed May 8 15:54:35 2002
@@ -285,4 +285,16 @@
#define die_if_kernel(msg, regs) \
__die_if_kernel(msg, regs, __FILE__ ":"__FUNCTION__, __LINE__)

+extern __inline__ int intr_on(void)
+{
+ unsigned long flags;
+ save_flags(flags);
+ return flags & 1;
+}
+
+extern __inline__ int intr_off(void)
+{
+ return ! intr_on();
+}
+
#endif /* _ASM_SYSTEM_H */
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