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 <linux/time64.h>
   8 #include <uapi/linux/sem.h>
   9
  10 struct task_struct;
  11
  12 /* One semaphore structure for each semaphore in the system. */
  13 struct sem {
  14         int     semval;         /* current value */
  15         /*
  16          * PID of the process that last modified the semaphore. For
  17          * Linux, specifically these are:
  18          *  - semop
  19          *  - semctl, via SETVAL and SETALL.
  20          *  - at task exit when performing undo adjustments (see exit_sem).
  21          */
  22         int     sempid;
  23         spinlock_t      lock;   /* spinlock for fine-grained semtimedop */
  24         struct list_head pending_alter; /* pending single-sop operations */
  25                                         /* that alter the semaphore */
  26         struct list_head pending_const; /* pending single-sop operations */
  27                                         /* that do not alter the semaphore*/
  28         time_t  sem_otime;      /* candidate for sem_otime */
  29 } ____cacheline_aligned_in_smp;
  30
  31 /* One sem_array data structure for each set of semaphores in the system. */
  32 struct sem_array {
  33         struct kern_ipc_perm    sem_perm;       /* permissions .. see ipc.h */
  34         time64_t                sem_ctime;      /* create/last semctl() time */
  35         struct list_head        pending_alter;  /* pending operations */
  36                                                 /* that alter the array */
  37         struct list_head        pending_const;  /* pending complex operations */
  38                                                 /* that do not alter semvals */
  39         struct list_head        list_id;        /* undo requests on this array */
  40         int                     sem_nsems;      /* no. of semaphores in array */
  41         int                     complex_count;  /* pending complex operations */
  42         unsigned int            use_global_lock;/* >0: global lock required */
  43
  44         struct sem              sems[];
  45 } __randomize_layout;
  46
  47 #ifdef CONFIG_SYSVIPC
  48
  49 struct sysv_sem {
  50         struct sem_undo_list *undo_list;
  51 };
  52
  53 extern int copy_semundo(unsigned long clone_flags, struct task_struct *tsk);
  54 extern void exit_sem(struct task_struct *tsk);
  55
  56 #else
  57
  58 struct sysv_sem {
  59         /* empty */
  60 };
  61
  62 static inline int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
  63 {
  64         return 0;
  65 }
  66
  67 static inline void exit_sem(struct task_struct *tsk)
  68 {
  69         return;
  70 }
  71 #endif
  72
  73 #endif /* _LINUX_SEM_H */