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- Merge the pgrpsess_lock and proctree_lock sx locks into one proctree_lock

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sx lock.  Trying to get the lock order between these locks was getting
  too complicated as the locking in wait1() was being fixed.
- leavepgrp() now requires an exclusive lock of proctree_lock to be held
  when it is called.
- fixjobc() no longer gets a shared lock of proctree_lock now that it
  requires an xlock be held by the caller.
- Locking notes in sys/proc.h are adjusted to note that everything that
  used to be protected by the pgrpsess_lock is now protected by the
  proctree_lock.
This commit is contained in:
John Baldwin 2002-04-16 17:03:05 +00:00
parent 6fe599457d
commit f089b57070
3 changed files with 17 additions and 30 deletions
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24
sys/kern/kern_proc.c
View File

@ -80,7 +80,6 @@ struct proclist allproc;
struct proclist zombproc;
struct sx allproc_lock;
struct sx proctree_lock;
struct sx pgrpsess_lock;
struct mtx pargs_ref_lock;
uma_zone_t proc_zone;
uma_zone_t ithread_zone;
@ -96,7 +95,6 @@ procinit()
sx_init(&allproc_lock, "allproc");
sx_init(&proctree_lock, "proctree");
sx_init(&pgrpsess_lock, "pgrpsess");
mtx_init(&pargs_ref_lock, "struct pargs.ref", NULL, MTX_DEF);
LIST_INIT(&allproc);
LIST_INIT(&zombproc);
@ -284,7 +282,7 @@ dopfind(pid)
/*
* Locate a process group by number.
* The caller must hold pgrpsess_lock.
* The caller must hold proctree_lock.
*/
struct pgrp *
pgfind(pgid)
@ -292,7 +290,7 @@ pgfind(pgid)
{
register struct pgrp *pgrp;
PGRPSESS_LOCK_ASSERT(SX_LOCKED);
sx_assert(&proctree_lock, SX_LOCKED);
LIST_FOREACH(pgrp, PGRPHASH(pgid), pg_hash) {
if (pgrp->pg_id == pgid) {
@ -317,7 +315,7 @@ enterpgrp(p, pgid, pgrp, sess)
{
struct pgrp *pgrp2;
PGRPSESS_LOCK_ASSERT(SX_XLOCKED);
sx_assert(&proctree_lock, SX_XLOCKED);
KASSERT(pgrp != NULL, ("enterpgrp: pgrp == NULL"));
KASSERT(p->p_pid == pgid,
@ -362,7 +360,7 @@ enterpgrp(p, pgid, pgrp, sess)
LIST_INIT(&pgrp->pg_members);
/*
* As we have an exclusive lock of pgrpsess_lock,
* As we have an exclusive lock of proctree_lock,
* this should not deadlock.
*/
LIST_INSERT_HEAD(PGRPHASH(pgid), pgrp, pg_hash);
@ -383,7 +381,8 @@ enterthispgrp(p, pgrp)
register struct proc *p;
struct pgrp *pgrp;
{
PGRPSESS_LOCK_ASSERT(SX_XLOCKED);
sx_assert(&proctree_lock, SX_XLOCKED);
PROC_LOCK_ASSERT(p, MA_NOTOWNED);
PGRP_LOCK_ASSERT(pgrp, MA_NOTOWNED);
PGRP_LOCK_ASSERT(p->p_pgrp, MA_NOTOWNED);
@ -411,7 +410,7 @@ doenterpgrp(p, pgrp)
{
struct pgrp *savepgrp;
PGRPSESS_LOCK_ASSERT(SX_XLOCKED);
sx_assert(&proctree_lock, SX_XLOCKED);
PROC_LOCK_ASSERT(p, MA_NOTOWNED);
PGRP_LOCK_ASSERT(pgrp, MA_NOTOWNED);
PGRP_LOCK_ASSERT(p->p_pgrp, MA_NOTOWNED);
@ -449,7 +448,7 @@ leavepgrp(p)
{
struct pgrp *savepgrp;
PGRPSESS_XLOCK();
sx_assert(&proctree_lock, SX_XLOCKED);
savepgrp = p->p_pgrp;
PGRP_LOCK(savepgrp);
PROC_LOCK(p);
@ -459,7 +458,6 @@ leavepgrp(p)
PGRP_UNLOCK(savepgrp);
if (LIST_EMPTY(&savepgrp->pg_members))
pgdelete(savepgrp);
PGRPSESS_XUNLOCK();
return (0);
}
@ -472,7 +470,7 @@ pgdelete(pgrp)
{
struct session *savesess;
PGRPSESS_LOCK_ASSERT(SX_XLOCKED);
sx_assert(&proctree_lock, SX_XLOCKED);
PGRP_LOCK_ASSERT(pgrp, MA_NOTOWNED);
SESS_LOCK_ASSERT(pgrp->pg_session, MA_NOTOWNED);
@ -520,7 +518,7 @@ fixjobc(p, pgrp, entering)
register struct pgrp *hispgrp;
register struct session *mysession;
PGRPSESS_LOCK_ASSERT(SX_LOCKED);
sx_assert(&proctree_lock, SX_LOCKED);
PROC_LOCK_ASSERT(p, MA_NOTOWNED);
PGRP_LOCK_ASSERT(pgrp, MA_NOTOWNED);
SESS_LOCK_ASSERT(pgrp->pg_session, MA_NOTOWNED);
@ -530,7 +528,6 @@ fixjobc(p, pgrp, entering)
* group; if so, adjust count for p's process group.
*/
mysession = pgrp->pg_session;
sx_slock(&proctree_lock);
if ((hispgrp = p->p_pptr->p_pgrp) != pgrp &&
hispgrp->pg_session == mysession) {
PGRP_LOCK(pgrp);
@ -564,7 +561,6 @@ fixjobc(p, pgrp, entering)
PGRP_UNLOCK(hispgrp);
}
}
sx_sunlock(&proctree_lock);
}
/*

1
sys/kern/subr_witness.c
View File

@ -187,7 +187,6 @@ static struct lock_list_entry w_locklistdata[LOCK_CHILDCOUNT];
static struct witness_order_list_entry order_lists[] = {
{ "Giant", &lock_class_mtx_sleep },
{ "pgrpsess", &lock_class_sx },
{ "proctree", &lock_class_sx },
{ "allproc", &lock_class_sx },
{ "process group", &lock_class_mtx_sleep },

22
sys/sys/proc.h
View File

@ -64,12 +64,12 @@
*
* List of locks
* (m) locked by s_mtx mtx
* (ps) locked by pgrpsess_lock sx
* (e) locked by proctree_lock sx
* (c) const until freeing
*/
struct session {
int s_count; /* (m) Ref cnt; pgrps in session. */
struct proc *s_leader; /* (m, ps) Session leader. */
struct proc *s_leader; /* (m + e) Session leader. */
struct vnode *s_ttyvp; /* (m) Vnode of controlling terminal. */
struct tty *s_ttyp; /* (m) Controlling terminal. */
pid_t s_sid; /* (c) Session ID. */
@ -83,12 +83,12 @@ struct session {
*
* List of locks
* (m) locked by pg_mtx mtx
* (ps) locked by pgrpsess_lock sx
* (e) locked by proctree_lock sx
* (c) const until freeing
*/
struct pgrp {
LIST_ENTRY(pgrp) pg_hash; /* (ps) Hash chain. */
LIST_HEAD(, proc) pg_members; /* (m, ps) Pointer to pgrp members. */
LIST_ENTRY(pgrp) pg_hash; /* (e) Hash chain. */
LIST_HEAD(, proc) pg_members; /* (m + e) Pointer to pgrp members. */
struct session *pg_session; /* (c) Pointer to session. */
struct sigiolst pg_sigiolst; /* (m) List of sigio sources. */
pid_t pg_id; /* (c) Pgrp id. */
@ -147,7 +147,6 @@ struct pargs {
* l - the attaching proc or attaching proc parent
* m - Giant
* n - not locked, lazy
* o - locked by pgrpsess_lock sx
* p - select lock (sellock)
*
* If the locking key specifies two identifiers (for example, p_pptr) then
@ -399,7 +398,7 @@ struct proc {
pid_t p_pid; /* (b) Process identifier. */
LIST_ENTRY(proc) p_hash; /* (d) Hash chain. */
LIST_ENTRY(proc) p_pglist; /* (g + o) List of processes in pgrp. */
LIST_ENTRY(proc) p_pglist; /* (g + e) List of processes in pgrp. */
struct proc *p_pptr; /* (c + e) Pointer to parent process. */
LIST_ENTRY(proc) p_sibling; /* (e) List of sibling processes. */
LIST_HEAD(, proc) p_children; /* (e) Pointer to list of children. */
@ -438,7 +437,7 @@ struct proc {
stack_t p_sigstk; /* (c) Stack ptr and on-stack flag. */
int p_magic; /* (b) Magic number. */
char p_comm[MAXCOMLEN + 1]; /* (b) Process name. */
struct pgrp *p_pgrp; /* (c + o) Pointer to process group. */
struct pgrp *p_pgrp; /* (c + e) Pointer to process group. */
struct sysentvec *p_sysent; /* (b) Syscall dispatch info. */
struct pargs *p_args; /* (c) Process arguments. */
/* End area that is copied on creation. */
@ -603,12 +602,6 @@ sigonstack(size_t sp)
#define PROC_LOCKED(p) mtx_owned(&(p)->p_mtx)
#define PROC_LOCK_ASSERT(p, type) mtx_assert(&(p)->p_mtx, (type))
#define PGRPSESS_SLOCK() sx_slock(&pgrpsess_lock)
#define PGRPSESS_XLOCK() sx_xlock(&pgrpsess_lock)
#define PGRPSESS_SUNLOCK() sx_sunlock(&pgrpsess_lock)
#define PGRPSESS_XUNLOCK() sx_xunlock(&pgrpsess_lock)
#define PGRPSESS_LOCK_ASSERT(type) sx_assert(&pgrpsess_lock, (type))
/* Lock and unlock a process group. */
#define PGRP_LOCK(pg) mtx_lock(&(pg)->pg_mtx)
#define PGRP_UNLOCK(pg) mtx_unlock(&(pg)->pg_mtx)
@ -673,7 +666,6 @@ extern u_long pgrphash;
extern struct sx allproc_lock;
extern struct sx proctree_lock;
extern struct sx pgrpsess_lock;
extern struct mtx pargs_ref_lock;
extern struct proc proc0; /* Process slot for swapper. */
extern struct thread thread0; /* Primary thread in proc0 */