These symbols, related to interrupt management, were introduced in this chapter:
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#include <linux/sched.h>,int request_irq(unsigned int irq, void (*handler)(), unsigned long flags, const char *device, void *dev_id);,void free_irq(unsigned int irq, void *dev_id); These calls are used to register and unregister an interrupt handler. Kernels older than 2.0 lack the
dev_idargument.-
SA_INTERRUPT,SA_SHIRQ,SA_SAMPLE_RANDOM Flags for request_irq.
SA_INTERRUPTrequests installation of a fast handler (as opposed to a slow one).SA_SHIRQinstalls a shared handler, and the third flag asserts that interrupt timestamps can be used to generate system entropy.- /proc/interrupts, /proc/stat
These filesystem nodes are used to report information about hardware interrupts and installed handlers.
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unsigned long probe_irq_on(void);,int probe_irq_off(unsigned long); These functions are used by the driver when it has to probe to determine what interrupt line is being used by a device. The result of probe_irq_on must be passed back to probe_irq_off after the interrupt has been generated. The return value of probe_irq_off is the detected interrupt number.
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void disable_irq(int irq);,void enable_irq(int irq); A driver can enable and disable interrupt reporting. If the hardware tries to generate an interrupt while interrupts are disabled, the interrupt is lost forever. Calling these functions from a top-half handler has no effect. A driver using a shared handler must not use these functions.
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#include <linux/interrupt.h>,void mark_bh(int nr); This function marks a bottom half for execution.
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#include <asm/bitops.h>,set_bit(nr, void *addr);,clear_bit(nr, void *addr);,change_bit(nr, void *addr);,test_bit(nr, void *addr); These functions atomically access bit values; they can be used for flags or lock variables. Using these functions prevents any race condition related to concurrent access to the bit.
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#include <asm/atomic.h>,typedef int atomic_t;,void atomic_add(atomic_t i, atomic_t *v);,void atomic_sub(atomic_t i, atomic_t *v);,void atomic_inc(atomic_t *v);,void atomic_dec(atomic_t *v);,int atomic_dec_and_test(atomic_t *v); These functions atomically access integer variables. To achieve a clean compile, the
atomic_tvariables must be accessed only through these functions.-
#include <linux/sched.h>,TASK_RUNNING,TASK_INTERRUPTIBLE,TASK_UNINTERRUPTIBLE The most commonly used values for
current->state. They are used as hints for schedule.-
void add_wait_queue(struct wait_queue ** p,,struct wait_queue * wait),void remove_wait_queue(struct wait_queue ** p,,struct wait_queue * wait),void __add_wait_queue(struct wait_queue ** p,,struct wait_queue * wait),void __remove_wait_queue(struct wait_queue ** p,,struct wait_queue * wait) The lowest-level functions that use wait queues. The leading underscores indicate a lower-level functionality, in which case interrupt reporting must already be disabled in the processor.