xref: /illumos-gate/usr/src/uts/common/sys/session.h (revision b4203d75)
17c478bd9Sstevel@tonic-gate /*
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217c478bd9Sstevel@tonic-gate /*
229acbbeafSnn  * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
237c478bd9Sstevel@tonic-gate  * Use is subject to license terms.
247c478bd9Sstevel@tonic-gate  */
257c478bd9Sstevel@tonic-gate 
267c478bd9Sstevel@tonic-gate /*	Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T	*/
27*b4203d75SMarcel Telka /*	  All Rights Reserved	*/
287c478bd9Sstevel@tonic-gate 
297c478bd9Sstevel@tonic-gate 
307c478bd9Sstevel@tonic-gate #ifndef _SYS_SESSION_H
317c478bd9Sstevel@tonic-gate #define	_SYS_SESSION_H
327c478bd9Sstevel@tonic-gate 
337c478bd9Sstevel@tonic-gate #ifdef	__cplusplus
347c478bd9Sstevel@tonic-gate extern "C" {
357c478bd9Sstevel@tonic-gate #endif
367c478bd9Sstevel@tonic-gate 
379acbbeafSnn /*
389acbbeafSnn  * Session structure overview.
399acbbeafSnn  *
409acbbeafSnn  * Currently, the only structure in the kernel which has a pointer to a
419acbbeafSnn  * session structures is the proc_t via the p_sessp pointer.  To
429acbbeafSnn  * access a session proc_t->p_sessp pointer a caller must hold either
439acbbeafSnn  * pidlock or p_splock.  These locks only protect the p_sessp pointer
449acbbeafSnn  * itself and do not protect any of the contents of the session structure.
459acbbeafSnn  * To prevent the contents of a the session structure from changing the
469acbbeafSnn  * caller must grab s_lock.
479acbbeafSnn  *
489acbbeafSnn  * No callers should ever update the contents of the session structure
499acbbeafSnn  * directly.  Only the session management code should ever modify the
509acbbeafSnn  * contents of the session structure.  When the session code attempts
519acbbeafSnn  * to modify the contents of a session structure it must hold multiple
529acbbeafSnn  * locks.  The locking order for all the locks that may need to be
539acbbeafSnn  * acquired is:
549acbbeafSnn  * 	sd_lock -> pidlock -> p_splock -> s_lock
559acbbeafSnn  *
569acbbeafSnn  * If a caller requires access to a session structure for long
579acbbeafSnn  * periods of time or across operations that may block it should
589acbbeafSnn  * use the tty_hold() and sess_hold() interfaces.
599acbbeafSnn  *
609acbbeafSnn  * sess_hold() returns a pointer to a session structure associated
619acbbeafSnn  * with the proc_t that was passed in.  It also increments the reference
629acbbeafSnn  * count associated with that session structure to ensure that it
639acbbeafSnn  * can't be freed until after the caller is done with it and calls
649acbbeafSnn  * sess_rele().  This hold doesn't actually protect any of the
659acbbeafSnn  * contents of the session structure.
669acbbeafSnn  *
679acbbeafSnn  * tty_hold() returns a pointer to a session structure associated
689acbbeafSnn  * with the curproc.  It also "locks" the contents of the session
699acbbeafSnn  * structure.  This hold should be used when the caller will be
709acbbeafSnn  * doing operations on a controlling tty associated with the session.
719acbbeafSnn  * This operation doesn an implicit sess_hold() so that the session
729acbbeafSnn  * structure can't be free'd until after the caller is done with it
739acbbeafSnn  * and invokes tty_rele().
749acbbeafSnn  *
759acbbeafSnn  * NOTE: Neither of these functions (sess_hold() or tty_hold())
769acbbeafSnn  * prevent a process from changing its session.  Once these functions
779acbbeafSnn  * return a session pointer, that session pointer may no longer be
789acbbeafSnn  * associated with the current process.  If a caller wants to prevent
799acbbeafSnn  * a process from changing its session then it must hold pidlock or
809acbbeafSnn  * p_splock.
819acbbeafSnn  */
829acbbeafSnn 
837c478bd9Sstevel@tonic-gate typedef struct sess {
849acbbeafSnn 	struct pid *s_sidp;		/* session ID info, never changes */
857c478bd9Sstevel@tonic-gate 
869acbbeafSnn 	kmutex_t s_lock;		/* protects everything below */
879acbbeafSnn 	uint_t s_ref; 			/* reference count */
889acbbeafSnn 	boolean_t s_sighuped;		/* ctty had sighup sent to it */
897c478bd9Sstevel@tonic-gate 
909acbbeafSnn 	boolean_t s_exit;		/* sesion leader is exiting */
919acbbeafSnn 	kcondvar_t s_exit_cv;		/* Condvar for s_exit */
927c478bd9Sstevel@tonic-gate 
939acbbeafSnn 	int s_cnt;			/* active users of this ctty */
949acbbeafSnn 	kcondvar_t s_cnt_cv;		/* Condvar for s_cnt */
957c478bd9Sstevel@tonic-gate 
969acbbeafSnn 	/*
979acbbeafSnn 	 * The following fields can only be updated while s_lock is held
989acbbeafSnn 	 * and s_cnt is 0.  (ie, no one has a tty_hold() on this session.)
999acbbeafSnn 	 */
1009acbbeafSnn 	dev_t s_dev;			/* tty's device number */
1019acbbeafSnn 	struct vnode *s_vp;		/* tty's vnode */
1029acbbeafSnn 	struct cred *s_cred;		/* allocation credentials */
1039acbbeafSnn } sess_t;
1047c478bd9Sstevel@tonic-gate 
1059acbbeafSnn #define	s_sid s_sidp->pid_id
1067c478bd9Sstevel@tonic-gate 
1079acbbeafSnn #if defined(_KERNEL)
1087c478bd9Sstevel@tonic-gate 
1099acbbeafSnn extern sess_t session0;
1107c478bd9Sstevel@tonic-gate 
1117c478bd9Sstevel@tonic-gate /* forward referenced structure tags */
1127c478bd9Sstevel@tonic-gate struct vnode;
1137c478bd9Sstevel@tonic-gate struct proc;
1149acbbeafSnn struct stdata;
1159acbbeafSnn 
1169acbbeafSnn extern void sess_hold(proc_t *p);
1179acbbeafSnn extern void sess_rele(sess_t *, boolean_t);
1189acbbeafSnn extern sess_t *tty_hold(void);
1199acbbeafSnn extern void tty_rele(sess_t *sp);
1209acbbeafSnn 
1217c478bd9Sstevel@tonic-gate 
1227c478bd9Sstevel@tonic-gate extern void sess_create(void);
1239acbbeafSnn extern int strctty(struct stdata *);
1249acbbeafSnn extern int freectty(boolean_t);
1257c478bd9Sstevel@tonic-gate extern dev_t cttydev(struct proc *);
1269acbbeafSnn extern void ctty_clear_sighuped(void);
1277c478bd9Sstevel@tonic-gate 
1287c478bd9Sstevel@tonic-gate #endif /* defined(_KERNEL) */
1297c478bd9Sstevel@tonic-gate 
1307c478bd9Sstevel@tonic-gate #ifdef	__cplusplus
1317c478bd9Sstevel@tonic-gate }
1327c478bd9Sstevel@tonic-gate #endif
1337c478bd9Sstevel@tonic-gate 
1347c478bd9Sstevel@tonic-gate #endif	/* _SYS_SESSION_H */
135