[PATCH] arch/mips/kernel/irq_cpu.c interrupt safety?

[William Jhun <wjhun@ayrnetworks.com>]

The mips_cpu_irq_*() routines in arch/mips/kernel/irq_cpu.c seem to not be
safe; {clear,set}_cp0_*() don't provide interrupt safety while changing the cp0
register. Is this not wrong? Is there a case where an interrupt handler may
change CP0 status? If so, the patch below (against linux_2_4) simply disables
interrupts during these operations.

Thanks,
Will

---
Index: arch/mips/kernel/irq_cpu.c
===================================================================
RCS file: /cvs/linux/arch/mips/kernel/irq_cpu.c,v
retrieving revision 1.2.2.2
diff -c -r1.2.2.2 irq_cpu.c
*** arch/mips/kernel/irq_cpu.c  2002/04/09 02:27:12     1.2.2.2
--- arch/mips/kernel/irq_cpu.c  2002/05/21 01:16:30
***************
*** 31,45 ****
  
  static void mips_cpu_irq_enable(unsigned int irq)
  {
        clear_cp0_cause( 1 << (irq - mips_cpu_irq_base + 8));
        set_cp0_status(1 << (irq - mips_cpu_irq_base + 8));
  }
  
! static void mips_cpu_irq_disable(unsigned int irq)
  {
        clear_cp0_status(1 << (irq - mips_cpu_irq_base + 8));
  }
  
  static unsigned int mips_cpu_irq_startup(unsigned int irq)
  {
        mips_cpu_irq_enable(irq);
--- 31,56 ----
  
  static void mips_cpu_irq_enable(unsigned int irq)
  {
+       unsigned long flags;
+       save_and_cli(flags);
        clear_cp0_cause( 1 << (irq - mips_cpu_irq_base + 8));
        set_cp0_status(1 << (irq - mips_cpu_irq_base + 8));
+       restore_flags(flags);
  }
  
! static void __mips_cpu_irq_disable(unsigned int irq)
  {
        clear_cp0_status(1 << (irq - mips_cpu_irq_base + 8));
  }
  
+ static void mips_cpu_irq_disable(unsigned int irq)
+ {
+       unsigned long flags;
+       save_and_cli(flags);
+       __mips_cpu_irq_disable(irq);
+       restore_flags(flags);
+ }
+ 
  static unsigned int mips_cpu_irq_startup(unsigned int irq)
  {
        mips_cpu_irq_enable(irq);
***************
*** 51,63 ****
  
  static void mips_cpu_irq_ack(unsigned int irq)
  {
!       /* although we attemp to clear the IP bit in cause reigster, I think
         * usually it is cleared by device (irq source)
         */
        clear_cp0_cause(1 << (irq - mips_cpu_irq_base + 8));
  
        /* disable this interrupt - so that we safe proceed to the handler */
!       mips_cpu_irq_disable(irq);
  }
  
  static void mips_cpu_irq_end(unsigned int irq)
--- 62,78 ----
  
  static void mips_cpu_irq_ack(unsigned int irq)
  {
!       unsigned long flags;
!       save_and_cli(flags);
! 
!       /* although we attempt to clear the IP bit in cause register, I think
         * usually it is cleared by device (irq source)
         */
        clear_cp0_cause(1 << (irq - mips_cpu_irq_base + 8));
  
        /* disable this interrupt - so that we safe proceed to the handler */
!       __mips_cpu_irq_disable(irq);
!       restore_flags(flags);
  }
  
  static void mips_cpu_irq_end(unsigned int irq)