include/linux/poll.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _LINUX_POLL_H
   3 #define _LINUX_POLL_H
   4
   5
   6 #include <linux/compiler.h>
   7 #include <linux/ktime.h>
   8 #include <linux/wait.h>
   9 #include <linux/string.h>
  10 #include <linux/fs.h>
  11 #include <linux/sysctl.h>
  12 #include <linux/uaccess.h>
  13 #include <uapi/linux/poll.h>
  14
  15 extern struct ctl_table epoll_table[]; /* for sysctl */
  16 /* ~832 bytes of stack space used max in sys_select/sys_poll before allocating
  17    additional memory. */
  18 #ifdef __clang__
  19 #define MAX_STACK_ALLOC 768
  20 #else
  21 #define MAX_STACK_ALLOC 832
  22 #endif
  23 #define FRONTEND_STACK_ALLOC    256
  24 #define SELECT_STACK_ALLOC      FRONTEND_STACK_ALLOC
  25 #define POLL_STACK_ALLOC        FRONTEND_STACK_ALLOC
  26 #define WQUEUES_STACK_ALLOC     (MAX_STACK_ALLOC - FRONTEND_STACK_ALLOC)
  27 #define N_INLINE_POLL_ENTRIES   (WQUEUES_STACK_ALLOC / sizeof(struct poll_table_entry))
  28
  29 #define DEFAULT_POLLMASK (POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM)
  30
  31 struct poll_table_struct;
  32
  33 /*
  34  * structures and helpers for f_op->poll implementations
  35  */
  36 typedef void (*poll_queue_proc)(struct file *, wait_queue_head_t *, struct poll_table_struct *);
  37
  38 /*
  39  * Do not touch the structure directly, use the access functions
  40  * poll_does_not_wait() and poll_requested_events() instead.
  41  */
  42 typedef struct poll_table_struct {
  43         poll_queue_proc _qproc;
  44         unsigned long _key;
  45 } poll_table;
  46
  47 static inline void poll_wait(struct file * filp, wait_queue_head_t * wait_address, poll_table *p)
  48 {
  49         if (p && p->_qproc && wait_address)
  50                 p->_qproc(filp, wait_address, p);
  51 }
  52
  53 /*
  54  * Return true if it is guaranteed that poll will not wait. This is the case
  55  * if the poll() of another file descriptor in the set got an event, so there
  56  * is no need for waiting.
  57  */
  58 static inline bool poll_does_not_wait(const poll_table *p)
  59 {
  60         return p == NULL || p->_qproc == NULL;
  61 }
  62
  63 /*
  64  * Return the set of events that the application wants to poll for.
  65  * This is useful for drivers that need to know whether a DMA transfer has
  66  * to be started implicitly on poll(). You typically only want to do that
  67  * if the application is actually polling for POLLIN and/or POLLOUT.
  68  */
  69 static inline unsigned long poll_requested_events(const poll_table *p)
  70 {
  71         return p ? p->_key : ~0UL;
  72 }
  73
  74 static inline void init_poll_funcptr(poll_table *pt, poll_queue_proc qproc)
  75 {
  76         pt->_qproc = qproc;
  77         pt->_key   = ~0UL; /* all events enabled */
  78 }
  79
  80 struct poll_table_entry {
  81         struct file *filp;
  82         unsigned long key;
  83         wait_queue_entry_t wait;
  84         wait_queue_head_t *wait_address;
  85 };
  86
  87 /*
  88  * Structures and helpers for select/poll syscall
  89  */
  90 struct poll_wqueues {
  91         poll_table pt;
  92         struct poll_table_page *table;
  93         struct task_struct *polling_task;
  94         int triggered;
  95         int error;
  96         int inline_index;
  97         struct poll_table_entry inline_entries[N_INLINE_POLL_ENTRIES];
  98 };
  99
 100 extern void poll_initwait(struct poll_wqueues *pwq);
 101 extern void poll_freewait(struct poll_wqueues *pwq);
 102 extern int poll_schedule_timeout(struct poll_wqueues *pwq, int state,
 103                                  ktime_t *expires, unsigned long slack);
 104 extern u64 select_estimate_accuracy(struct timespec64 *tv);
 105
 106 #define MAX_INT64_SECONDS (((s64)(~((u64)0)>>1)/HZ)-1)
 107
 108 extern int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
 109                            fd_set __user *exp, struct timespec64 *end_time);
 110
 111 extern int poll_select_set_timeout(struct timespec64 *to, time64_t sec,
 112                                    long nsec);
 113
 114 #endif /* _LINUX_POLL_H */