include/linux/sem.h

   1 #ifndef _LINUX_SEM_H
   2 #define _LINUX_SEM_H
   3
   4 #include <linux/atomic.h>
   5 #include <linux/rcupdate.h>
   6 #include <linux/cache.h>
   7 #include <uapi/linux/sem.h>
   8
   9 struct task_struct;
  10
  11 /* One semaphore structure for each semaphore in the system. */
  12 struct sem {
  13         int     semval;         /* current value */
  14         /*
  15          * PID of the process that last modified the semaphore. For
  16          * Linux, specifically these are:
  17          *  - semop
  18          *  - semctl, via SETVAL and SETALL.
  19          *  - at task exit when performing undo adjustments (see exit_sem).
  20          */
  21         int     sempid;
  22         spinlock_t      lock;   /* spinlock for fine-grained semtimedop */
  23         struct list_head pending_alter; /* pending single-sop operations */
  24                                         /* that alter the semaphore */
  25         struct list_head pending_const; /* pending single-sop operations */
  26                                         /* that do not alter the semaphore*/
  27         time_t  sem_otime;      /* candidate for sem_otime */
  28 } ____cacheline_aligned_in_smp;
  29
  30 /* One sem_array data structure for each set of semaphores in the system. */
  31 struct sem_array {
  32         struct kern_ipc_perm    sem_perm;       /* permissions .. see ipc.h */
  33         time_t                  sem_ctime;      /* create/last semctl() time */
  34         struct list_head        pending_alter;  /* pending operations */
  35                                                 /* that alter the array */
  36         struct list_head        pending_const;  /* pending complex operations */
  37                                                 /* that do not alter semvals */
  38         struct list_head        list_id;        /* undo requests on this array */
  39         int                     sem_nsems;      /* no. of semaphores in array */
  40         int                     complex_count;  /* pending complex operations */
  41         unsigned int            use_global_lock;/* >0: global lock required */
  42
  43         struct sem              sems[];
  44 } __randomize_layout;
  45
  46 #ifdef CONFIG_SYSVIPC
  47
  48 struct sysv_sem {
  49         struct sem_undo_list *undo_list;
  50 };
  51
  52 extern int copy_semundo(unsigned long clone_flags, struct task_struct *tsk);
  53 extern void exit_sem(struct task_struct *tsk);
  54
  55 #else
  56
  57 struct sysv_sem {
  58         /* empty */
  59 };
  60
  61 static inline int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
  62 {
  63         return 0;
  64 }
  65
  66 static inline void exit_sem(struct task_struct *tsk)
  67 {
  68         return;
  69 }
  70 #endif
  71
  72 #endif /* _LINUX_SEM_H */