include/linux/sem.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _LINUX_SEM_H
   3 #define _LINUX_SEM_H
   4
   5 #include <linux/atomic.h>
   6 #include <linux/rcupdate.h>
   7 #include <linux/cache.h>
   8 #include <linux/time64.h>
   9 #include <uapi/linux/sem.h>
  10
  11 struct task_struct;
  12
  13 /* One semaphore structure for each semaphore in the system. */
  14 struct sem {
  15         int     semval;         /* current value */
  16         /*
  17          * PID of the process that last modified the semaphore. For
  18          * Linux, specifically these are:
  19          *  - semop
  20          *  - semctl, via SETVAL and SETALL.
  21          *  - at task exit when performing undo adjustments (see exit_sem).
  22          */
  23         int     sempid;
  24         spinlock_t      lock;   /* spinlock for fine-grained semtimedop */
  25         struct list_head pending_alter; /* pending single-sop operations */
  26                                         /* that alter the semaphore */
  27         struct list_head pending_const; /* pending single-sop operations */
  28                                         /* that do not alter the semaphore*/
  29         time_t  sem_otime;      /* candidate for sem_otime */
  30 } ____cacheline_aligned_in_smp;
  31
  32 /* One sem_array data structure for each set of semaphores in the system. */
  33 struct sem_array {
  34         struct kern_ipc_perm    sem_perm;       /* permissions .. see ipc.h */
  35         time64_t                sem_ctime;      /* create/last semctl() time */
  36         struct list_head        pending_alter;  /* pending operations */
  37                                                 /* that alter the array */
  38         struct list_head        pending_const;  /* pending complex operations */
  39                                                 /* that do not alter semvals */
  40         struct list_head        list_id;        /* undo requests on this array */
  41         int                     sem_nsems;      /* no. of semaphores in array */
  42         int                     complex_count;  /* pending complex operations */
  43         unsigned int            use_global_lock;/* >0: global lock required */
  44
  45         struct sem              sems[];
  46 } __randomize_layout;
  47
  48 #ifdef CONFIG_SYSVIPC
  49
  50 struct sysv_sem {
  51         struct sem_undo_list *undo_list;
  52 };
  53
  54 extern int copy_semundo(unsigned long clone_flags, struct task_struct *tsk);
  55 extern void exit_sem(struct task_struct *tsk);
  56
  57 #else
  58
  59 struct sysv_sem {
  60         /* empty */
  61 };
  62
  63 static inline int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
  64 {
  65         return 0;
  66 }
  67
  68 static inline void exit_sem(struct task_struct *tsk)
  69 {
  70         return;
  71 }
  72 #endif
  73
  74 #endif /* _LINUX_SEM_H */