diff options
Diffstat (limited to 'linux/dev/arch/i386/kernel/irq.c')
| -rw-r--r-- | linux/dev/arch/i386/kernel/irq.c | 278 |
1 files changed, 278 insertions, 0 deletions
diff --git a/linux/dev/arch/i386/kernel/irq.c b/linux/dev/arch/i386/kernel/irq.c index e9dfe6a..4bed353 100644 --- a/linux/dev/arch/i386/kernel/irq.c +++ b/linux/dev/arch/i386/kernel/irq.c @@ -45,12 +45,19 @@ #include <asm/bitops.h> #include <asm/irq.h> #include <asm/io.h> +#include <asm/hardirq.h> extern int linux_timer_intr (void); extern spl_t splhigh (void); extern spl_t spl0 (void); extern void form_pic_mask (void); +#if 0 +/* XXX: This is the way it's done in linux 2.2. GNU Mach currently uses intr_count. It should be made using local_{bh/irq}_count instead (through hardirq_enter/exit) for SMP support. */ +unsigned int local_bh_count[NR_CPUS]; +unsigned int local_irq_count[NR_CPUS]; +#endif + /* * XXX Move this into more suitable place... * Set if the machine has an EISA bus. @@ -407,6 +414,277 @@ reserve_mach_irqs (void) } } +#ifdef __SMP__ +unsigned char global_irq_holder = NO_PROC_ID; +unsigned volatile int global_irq_lock; +atomic_t global_irq_count; + +atomic_t global_bh_count; +atomic_t global_bh_lock; + +/* + * "global_cli()" is a special case, in that it can hold the + * interrupts disabled for a longish time, and also because + * we may be doing TLB invalidates when holding the global + * IRQ lock for historical reasons. Thus we may need to check + * SMP invalidate events specially by hand here (but not in + * any normal spinlocks) + */ +#if 0 +/* XXX: check how Mach handles this */ +static inline void check_smp_invalidate(int cpu) +{ + if (test_bit(cpu, &smp_invalidate_needed)) { + clear_bit(cpu, &smp_invalidate_needed); + local_flush_tlb(); + } +} +#endif + +static void show(char * str) +{ + int i; + unsigned long *stack; + int cpu = smp_processor_id(); + extern char *get_options(char *str, int *ints); + + printk("\n%s, CPU %d:\n", str, cpu); + printk("irq: %d [%d %d]\n", + atomic_read(&global_irq_count), local_irq_count[0], local_irq_count[1]); + printk("bh: %d [%d %d]\n", + atomic_read(&global_bh_count), local_bh_count[0], local_bh_count[1]); + stack = (unsigned long *) &stack; + for (i = 40; i ; i--) { + unsigned long x = *++stack; + //if (x > (unsigned long) &get_options && x < (unsigned long) &vsprintf) { + printk("<[%08lx]> ", x); + //} + } +} + +#define MAXCOUNT 100000000 + +static inline void wait_on_bh(void) +{ + int count = MAXCOUNT; + do { + if (!--count) { + show("wait_on_bh"); + count = ~0; + } + /* nothing .. wait for the other bh's to go away */ + } while (atomic_read(&global_bh_count) != 0); +} + +/* + * I had a lockup scenario where a tight loop doing + * spin_unlock()/spin_lock() on CPU#1 was racing with + * spin_lock() on CPU#0. CPU#0 should have noticed spin_unlock(), but + * apparently the spin_unlock() information did not make it + * through to CPU#0 ... nasty, is this by design, do we have to limit + * 'memory update oscillation frequency' artificially like here? + * + * Such 'high frequency update' races can be avoided by careful design, but + * some of our major constructs like spinlocks use similar techniques, + * it would be nice to clarify this issue. Set this define to 0 if you + * want to check whether your system freezes. I suspect the delay done + * by SYNC_OTHER_CORES() is in correlation with 'snooping latency', but + * i thought that such things are guaranteed by design, since we use + * the 'LOCK' prefix. + */ +#define SUSPECTED_CPU_OR_CHIPSET_BUG_WORKAROUND 1 + +#if SUSPECTED_CPU_OR_CHIPSET_BUG_WORKAROUND +# define SYNC_OTHER_CORES(x) udelay(x+1) +#else +/* + * We have to allow irqs to arrive between __sti and __cli + */ +# define SYNC_OTHER_CORES(x) __asm__ __volatile__ ("nop") +#endif + +static inline void wait_on_irq(int cpu) +{ + int count = MAXCOUNT; + + for (;;) { + + /* + * Wait until all interrupts are gone. Wait + * for bottom half handlers unless we're + * already executing in one.. + */ + if (!atomic_read(&global_irq_count)) { + if (local_bh_count[cpu] || !atomic_read(&global_bh_count)) + break; + } + + /* Duh, we have to loop. Release the lock to avoid deadlocks */ + clear_bit(0,&global_irq_lock); + + for (;;) { + if (!--count) { + show("wait_on_irq"); + count = ~0; + } + __sti(); + SYNC_OTHER_CORES(cpu); + __cli(); + //check_smp_invalidate(cpu); + if (atomic_read(&global_irq_count)) + continue; + if (global_irq_lock) + continue; + if (!local_bh_count[cpu] && atomic_read(&global_bh_count)) + continue; + if (!test_and_set_bit(0,&global_irq_lock)) + break; + } + } +} + +/* + * This is called when we want to synchronize with + * bottom half handlers. We need to wait until + * no other CPU is executing any bottom half handler. + * + * Don't wait if we're already running in an interrupt + * context or are inside a bh handler. + */ +void synchronize_bh(void) +{ + if (atomic_read(&global_bh_count) && !in_interrupt()) + wait_on_bh(); +} + +/* + * This is called when we want to synchronize with + * interrupts. We may for example tell a device to + * stop sending interrupts: but to make sure there + * are no interrupts that are executing on another + * CPU we need to call this function. + */ +void synchronize_irq(void) +{ + if (atomic_read(&global_irq_count)) { + /* Stupid approach */ + cli(); + sti(); + } +} + +static inline void get_irqlock(int cpu) +{ + if (test_and_set_bit(0,&global_irq_lock)) { + /* do we already hold the lock? */ + if ((unsigned char) cpu == global_irq_holder) + return; + /* Uhhuh.. Somebody else got it. Wait.. */ + do { + do { + //check_smp_invalidate(cpu); + } while (test_bit(0,&global_irq_lock)); + } while (test_and_set_bit(0,&global_irq_lock)); + } + /* + * We also to make sure that nobody else is running + * in an interrupt context. + */ + wait_on_irq(cpu); + + /* + * Ok, finally.. + */ + global_irq_holder = cpu; +} + +#define EFLAGS_IF_SHIFT 9 + +/* + * A global "cli()" while in an interrupt context + * turns into just a local cli(). Interrupts + * should use spinlocks for the (very unlikely) + * case that they ever want to protect against + * each other. + * + * If we already have local interrupts disabled, + * this will not turn a local disable into a + * global one (problems with spinlocks: this makes + * save_flags+cli+sti usable inside a spinlock). + */ +void __global_cli(void) +{ + unsigned int flags; + + __save_flags(flags); + if (flags & (1 << EFLAGS_IF_SHIFT)) { + int cpu = smp_processor_id(); + __cli(); + if (!local_irq_count[cpu]) + get_irqlock(cpu); + } +} + +void __global_sti(void) +{ + int cpu = smp_processor_id(); + + if (!local_irq_count[cpu]) + release_irqlock(cpu); + __sti(); +} + +/* + * SMP flags value to restore to: + * 0 - global cli + * 1 - global sti + * 2 - local cli + * 3 - local sti + */ +unsigned long __global_save_flags(void) +{ + int retval; + int local_enabled; + unsigned long flags; + + __save_flags(flags); + local_enabled = (flags >> EFLAGS_IF_SHIFT) & 1; + /* default to local */ + retval = 2 + local_enabled; + + /* check for global flags if we're not in an interrupt */ + if (!local_irq_count[smp_processor_id()]) { + if (local_enabled) + retval = 1; + if (global_irq_holder == (unsigned char) smp_processor_id()) + retval = 0; + } + return retval; +} + +void __global_restore_flags(unsigned long flags) +{ + switch (flags) { + case 0: + __global_cli(); + break; + case 1: + __global_sti(); + break; + case 2: + __cli(); + break; + case 3: + __sti(); + break; + default: + printk("global_restore_flags: %08lx (%08lx)\n", + flags, (&flags)[-1]); + } +} + +#endif + static int (*old_clock_handler) (); static int old_clock_pri; |