diff options
Diffstat (limited to 'arch/alpha/kernel/irq_smp.c')
| -rw-r--r-- | arch/alpha/kernel/irq_smp.c | 250 |
1 files changed, 250 insertions, 0 deletions
diff --git a/arch/alpha/kernel/irq_smp.c b/arch/alpha/kernel/irq_smp.c new file mode 100644 index 000000000..90a3c30b2 --- /dev/null +++ b/arch/alpha/kernel/irq_smp.c @@ -0,0 +1,250 @@ +/* + * linux/arch/alpha/kernel/irq_smp.c + * + */ + +#include <linux/kernel.h> +#include <linux/signal.h> +#include <linux/sched.h> +#include <linux/interrupt.h> +#include <linux/random.h> +#include <linux/init.h> +#include <linux/delay.h> +#include <linux/irq.h> + +#include <asm/system.h> +#include <asm/io.h> + + +/* Who has global_irq_lock. */ +int global_irq_holder = NO_PROC_ID; + +/* This protects IRQ's. */ +spinlock_t global_irq_lock = SPIN_LOCK_UNLOCKED; + +/* Global IRQ locking depth. */ +static void *previous_irqholder = NULL; + +#define MAXCOUNT 100000000 + + +static void +show(char * str, void *where) +{ +#if 0 + int i; + unsigned long *stack; +#endif + int cpu = smp_processor_id(); + + printk("\n%s, CPU %d: %p\n", str, cpu, where); + printk("irq: %d [%d %d]\n", + irqs_running(), + cpu_data[0].irq_count, + cpu_data[1].irq_count); + + printk("bh: %d [%d %d]\n", + spin_is_locked(&global_bh_lock) ? 1 : 0, + cpu_data[0].bh_count, + cpu_data[1].bh_count); +#if 0 + stack = (unsigned long *) &str; + for (i = 40; i ; i--) { + unsigned long x = *++stack; + if (x > (unsigned long) &init_task_union && + x < (unsigned long) &vsprintf) { + printk("<[%08lx]> ", x); + } + } +#endif +} + +static inline void +wait_on_irq(int cpu, void *where) +{ + int count = MAXCOUNT; + + for (;;) { + + /* + * Wait until all interrupts are gone. Wait + * for bottom half handlers unless we're + * already executing in one.. + */ + if (!irqs_running()) { + if (local_bh_count(cpu) + || !spin_is_locked(&global_bh_lock)) + break; + } + + /* Duh, we have to loop. Release the lock to avoid deadlocks */ + spin_unlock(&global_irq_lock); + + for (;;) { + if (!--count) { + show("wait_on_irq", where); + count = MAXCOUNT; + } + __sti(); + udelay(1); /* make sure to run pending irqs */ + __cli(); + + if (irqs_running()) + continue; + if (spin_is_locked(&global_irq_lock)) + continue; + if (!local_bh_count(cpu) + && spin_is_locked(&global_bh_lock)) + continue; + if (spin_trylock(&global_irq_lock)) + break; + } + } +} + +static inline void +get_irqlock(int cpu, void* where) +{ + if (!spin_trylock(&global_irq_lock)) { + /* Do we already hold the lock? */ + if (cpu == global_irq_holder) + return; + /* Uhhuh.. Somebody else got it. Wait. */ + spin_lock(&global_irq_lock); + } + + /* + * Ok, we got the lock bit. + * But that's actually just the easy part.. Now + * we need to make sure that nobody else is running + * in an interrupt context. + */ + wait_on_irq(cpu, where); + + /* + * Finally. + */ +#if DEBUG_SPINLOCK + global_irq_lock.task = current; + global_irq_lock.previous = where; +#endif + global_irq_holder = cpu; + previous_irqholder = where; +} + +void +__global_cli(void) +{ + int cpu = smp_processor_id(); + void *where = __builtin_return_address(0); + + /* + * Maximize ipl. If ipl was previously 0 and if this thread + * is not in an irq, then take global_irq_lock. + */ + if (swpipl(IPL_MAX) == IPL_MIN && !local_irq_count(cpu)) + get_irqlock(cpu, where); +} + +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; + int cpu = smp_processor_id(); + + __save_flags(flags); + local_enabled = (!(flags & 7)); + /* default to local */ + retval = 2 + local_enabled; + + /* Check for global flags if we're not in an interrupt. */ + if (!local_irq_count(cpu)) { + if (local_enabled) + retval = 1; + if (global_irq_holder == cpu) + 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(KERN_ERR "global_restore_flags: %08lx (%p)\n", + flags, __builtin_return_address(0)); + } +} + +/* + * From its use, I infer that synchronize_irq() stalls a thread until + * the effects of a command to an external device are known to have + * taken hold. Typically, the command is to stop sending interrupts. + * The strategy here is wait until there is at most one processor + * (this one) in an irq. The memory barrier serializes the write to + * the device and the subsequent accesses of global_irq_count. + * --jmartin + */ +#define DEBUG_SYNCHRONIZE_IRQ 0 + +void +synchronize_irq(void) +{ +#if 0 + /* Joe's version. */ + int cpu = smp_processor_id(); + int local_count; + int global_count; + int countdown = 1<<24; + void *where = __builtin_return_address(0); + + mb(); + do { + local_count = local_irq_count(cpu); + global_count = atomic_read(&global_irq_count); + if (DEBUG_SYNCHRONIZE_IRQ && (--countdown == 0)) { + printk("%d:%d/%d\n", cpu, local_count, global_count); + show("synchronize_irq", where); + break; + } + } while (global_count != local_count); +#else + /* Jay's version. */ + if (irqs_running()) { + cli(); + sti(); + } +#endif +} |