freebsd-dev/sys/kern/kern_fork.c

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/*
* Copyright (c) 1982, 1986, 1989, 1991, 1993
* The Regents of the University of California. All rights reserved.
* (c) UNIX System Laboratories, Inc.
* All or some portions of this file are derived from material licensed
* to the University of California by American Telephone and Telegraph
* Co. or Unix System Laboratories, Inc. and are reproduced herein with
* the permission of UNIX System Laboratories, Inc.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* @(#)kern_fork.c 8.6 (Berkeley) 4/8/94
*/
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#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_ktrace.h"
#include "opt_mac.h"
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#include <sys/param.h>
#include <sys/systm.h>
#include <sys/sysproto.h>
#include <sys/eventhandler.h>
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#include <sys/filedesc.h>
#include <sys/kernel.h>
#include <sys/kthread.h>
#include <sys/sysctl.h>
Rework the witness code to work with sx locks as well as mutexes. - Introduce lock classes and lock objects. Each lock class specifies a name and set of flags (or properties) shared by all locks of a given type. Currently there are three lock classes: spin mutexes, sleep mutexes, and sx locks. A lock object specifies properties of an additional lock along with a lock name and all of the extra stuff needed to make witness work with a given lock. This abstract lock stuff is defined in sys/lock.h. The lockmgr constants, types, and prototypes have been moved to sys/lockmgr.h. For temporary backwards compatability, sys/lock.h includes sys/lockmgr.h. - Replace proc->p_spinlocks with a per-CPU list, PCPU(spinlocks), of spin locks held. By making this per-cpu, we do not have to jump through magic hoops to deal with sched_lock changing ownership during context switches. - Replace proc->p_heldmtx, formerly a list of held sleep mutexes, with proc->p_sleeplocks, which is a list of held sleep locks including sleep mutexes and sx locks. - Add helper macros for logging lock events via the KTR_LOCK KTR logging level so that the log messages are consistent. - Add some new flags that can be passed to mtx_init(): - MTX_NOWITNESS - specifies that this lock should be ignored by witness. This is used for the mutex that blocks a sx lock for example. - MTX_QUIET - this is not new, but you can pass this to mtx_init() now and no events will be logged for this lock, so that one doesn't have to change all the individual mtx_lock/unlock() operations. - All lock objects maintain an initialized flag. Use this flag to export a mtx_initialized() macro that can be safely called from drivers. Also, we on longer walk the all_mtx list if MUTEX_DEBUG is defined as witness performs the corresponding checks using the initialized flag. - The lock order reversal messages have been improved to output slightly more accurate file and line numbers.
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#include <sys/lock.h>
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#include <sys/malloc.h>
#include <sys/mutex.h>
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#include <sys/proc.h>
#include <sys/pioctl.h>
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#include <sys/resourcevar.h>
#include <sys/sched.h>
#include <sys/syscall.h>
#include <sys/vmmeter.h>
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#include <sys/vnode.h>
#include <sys/acct.h>
#include <sys/mac.h>
#include <sys/ktr.h>
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#include <sys/ktrace.h>
#include <sys/unistd.h>
#include <sys/sx.h>
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#include <vm/vm.h>
#include <vm/pmap.h>
#include <vm/vm_map.h>
#include <vm/vm_extern.h>
#include <vm/uma.h>
#include <sys/user.h>
#include <machine/critical.h>
#ifndef _SYS_SYSPROTO_H_
struct fork_args {
int dummy;
};
#endif
static int forksleep; /* Place for fork1() to sleep on. */
/*
* MPSAFE
*/
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/* ARGSUSED */
int
fork(td, uap)
struct thread *td;
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struct fork_args *uap;
{
int error;
struct proc *p2;
error = fork1(td, RFFDG | RFPROC, 0, &p2);
if (error == 0) {
td->td_retval[0] = p2->p_pid;
td->td_retval[1] = 0;
}
return (error);
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}
/*
* MPSAFE
*/
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/* ARGSUSED */
int
vfork(td, uap)
struct thread *td;
struct vfork_args *uap;
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{
int error;
struct proc *p2;
error = fork1(td, RFFDG | RFPROC | RFPPWAIT | RFMEM, 0, &p2);
if (error == 0) {
td->td_retval[0] = p2->p_pid;
td->td_retval[1] = 0;
}
return (error);
}
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/*
* MPSAFE
*/
int
rfork(td, uap)
struct thread *td;
struct rfork_args *uap;
{
struct proc *p2;
int error;
/* Don't allow kernel-only flags. */
if ((uap->flags & RFKERNELONLY) != 0)
return (EINVAL);
error = fork1(td, uap->flags, 0, &p2);
if (error == 0) {
td->td_retval[0] = p2 ? p2->p_pid : 0;
td->td_retval[1] = 0;
}
return (error);
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}
int nprocs = 1; /* process 0 */
int lastpid = 0;
SYSCTL_INT(_kern, OID_AUTO, lastpid, CTLFLAG_RD, &lastpid, 0,
"Last used PID");
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/*
* Random component to lastpid generation. We mix in a random factor to make
* it a little harder to predict. We sanity check the modulus value to avoid
* doing it in critical paths. Don't let it be too small or we pointlessly
* waste randomness entropy, and don't let it be impossibly large. Using a
* modulus that is too big causes a LOT more process table scans and slows
* down fork processing as the pidchecked caching is defeated.
*/
static int randompid = 0;
static int
sysctl_kern_randompid(SYSCTL_HANDLER_ARGS)
{
int error, pid;
error = sysctl_wire_old_buffer(req, sizeof(int));
if (error != 0)
return(error);
sx_xlock(&allproc_lock);
pid = randompid;
error = sysctl_handle_int(oidp, &pid, 0, req);
if (error == 0 && req->newptr != NULL) {
if (pid < 0 || pid > PID_MAX - 100) /* out of range */
pid = PID_MAX - 100;
else if (pid < 2) /* NOP */
pid = 0;
else if (pid < 100) /* Make it reasonable */
pid = 100;
randompid = pid;
}
sx_xunlock(&allproc_lock);
return (error);
}
SYSCTL_PROC(_kern, OID_AUTO, randompid, CTLTYPE_INT|CTLFLAG_RW,
0, 0, sysctl_kern_randompid, "I", "Random PID modulus");
int
fork1(td, flags, pages, procp)
struct thread *td;
int flags;
int pages;
struct proc **procp;
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{
struct proc *p1, *p2, *pptr;
uid_t uid;
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struct proc *newproc;
int ok, trypid;
static int curfail, pidchecked = 0;
static struct timeval lastfail;
struct filedesc *fd;
struct filedesc_to_leader *fdtol;
struct thread *td2;
struct ksegrp *kg2;
struct sigacts *newsigacts;
int error;
/* Can't copy and clear. */
if ((flags & (RFFDG|RFCFDG)) == (RFFDG|RFCFDG))
return (EINVAL);
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p1 = td->td_proc;
/*
* Here we don't create a new process, but we divorce
* certain parts of a process from itself.
*/
if ((flags & RFPROC) == 0) {
vm_forkproc(td, NULL, NULL, flags);
/*
* Close all file descriptors.
*/
if (flags & RFCFDG) {
struct filedesc *fdtmp;
FILEDESC_LOCK(td->td_proc->p_fd);
fdtmp = fdinit(td->td_proc->p_fd);
FILEDESC_UNLOCK(td->td_proc->p_fd);
fdfree(td);
p1->p_fd = fdtmp;
}
/*
* Unshare file descriptors (from parent).
*/
if (flags & RFFDG) {
FILEDESC_LOCK(p1->p_fd);
if (p1->p_fd->fd_refcnt > 1) {
struct filedesc *newfd;
newfd = fdcopy(td->td_proc->p_fd);
FILEDESC_UNLOCK(p1->p_fd);
fdfree(td);
p1->p_fd = newfd;
} else
FILEDESC_UNLOCK(p1->p_fd);
}
*procp = NULL;
return (0);
}
/*
* Note 1:1 allows for forking with one thread coming out on the
* other side with the expectation that the process is about to
* exec.
*/
if (p1->p_flag & P_HADTHREADS) {
/*
* Idle the other threads for a second.
* Since the user space is copied, it must remain stable.
* In addition, all threads (from the user perspective)
* need to either be suspended or in the kernel,
* where they will try restart in the parent and will
* be aborted in the child.
*/
PROC_LOCK(p1);
if (thread_single(SINGLE_NO_EXIT)) {
/* Abort. Someone else is single threading before us. */
PROC_UNLOCK(p1);
return (ERESTART);
}
PROC_UNLOCK(p1);
/*
* All other activity in this process
* is now suspended at the user boundary,
* (or other safe places if we think of any).
*/
}
/* Allocate new proc. */
newproc = uma_zalloc(proc_zone, M_WAITOK);
#ifdef MAC
mac_init_proc(newproc);
#endif
knlist_init(&newproc->p_klist, &newproc->p_mtx);
/* We have to lock the process tree while we look for a pid. */
sx_slock(&proctree_lock);
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/*
* Although process entries are dynamically created, we still keep
* a global limit on the maximum number we will create. Don't allow
* a nonprivileged user to use the last ten processes; don't let root
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* exceed the limit. The variable nprocs is the current number of
* processes, maxproc is the limit.
*/
sx_xlock(&allproc_lock);
uid = td->td_ucred->cr_ruid;
if ((nprocs >= maxproc - 10 &&
suser_cred(td->td_ucred, SUSER_RUID) != 0) ||
nprocs >= maxproc) {
error = EAGAIN;
goto fail;
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}
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/*
* Increment the count of procs running with this uid. Don't allow
* a nonprivileged user to exceed their current limit.
*/
PROC_LOCK(p1);
ok = chgproccnt(td->td_ucred->cr_ruidinfo, 1,
Locking for the per-process resource limits structure. - struct plimit includes a mutex to protect a reference count. The plimit structure is treated similarly to struct ucred in that is is always copy on write, so having a reference to a structure is sufficient to read from it without needing a further lock. - The proc lock protects the p_limit pointer and must be held while reading limits from a process to keep the limit structure from changing out from under you while reading from it. - Various global limits that are ints are not protected by a lock since int writes are atomic on all the archs we support and thus a lock wouldn't buy us anything. - All accesses to individual resource limits from a process are abstracted behind a simple lim_rlimit(), lim_max(), and lim_cur() API that return either an rlimit, or the current or max individual limit of the specified resource from a process. - dosetrlimit() was renamed to kern_setrlimit() to match existing style of other similar syscall helper functions. - The alpha OSF/1 compat layer no longer calls getrlimit() and setrlimit() (it didn't used the stackgap when it should have) but uses lim_rlimit() and kern_setrlimit() instead. - The svr4 compat no longer uses the stackgap for resource limits calls, but uses lim_rlimit() and kern_setrlimit() instead. - The ibcs2 compat no longer uses the stackgap for resource limits. It also no longer uses the stackgap for accessing sysctl's for the ibcs2_sysconf() syscall but uses kernel_sysctl() instead. As a result, ibcs2_sysconf() no longer needs Giant. - The p_rlimit macro no longer exists. Submitted by: mtm (mostly, I only did a few cleanups and catchups) Tested on: i386 Compiled on: alpha, amd64
2004-02-04 21:52:57 +00:00
(uid != 0) ? lim_cur(p1, RLIMIT_NPROC) : 0);
PROC_UNLOCK(p1);
if (!ok) {
error = EAGAIN;
goto fail;
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}
/*
* Increment the nprocs resource before blocking can occur. There
* are hard-limits as to the number of processes that can run.
*/
nprocs++;
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/*
* Find an unused process ID. We remember a range of unused IDs
* ready to use (from lastpid+1 through pidchecked-1).
*
* If RFHIGHPID is set (used during system boot), do not allocate
* low-numbered pids.
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*/
trypid = lastpid + 1;
if (flags & RFHIGHPID) {
if (trypid < 10)
trypid = 10;
} else {
if (randompid)
trypid += arc4random() % randompid;
}
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retry:
/*
* If the process ID prototype has wrapped around,
* restart somewhat above 0, as the low-numbered procs
* tend to include daemons that don't exit.
*/
if (trypid >= PID_MAX) {
trypid = trypid % PID_MAX;
if (trypid < 100)
trypid += 100;
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pidchecked = 0;
}
if (trypid >= pidchecked) {
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int doingzomb = 0;
pidchecked = PID_MAX;
/*
* Scan the active and zombie procs to check whether this pid
* is in use. Remember the lowest pid that's greater
* than trypid, so we can avoid checking for a while.
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*/
p2 = LIST_FIRST(&allproc);
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again:
for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) {
PROC_LOCK(p2);
while (p2->p_pid == trypid ||
(p2->p_pgrp != NULL &&
(p2->p_pgrp->pg_id == trypid ||
(p2->p_session != NULL &&
p2->p_session->s_sid == trypid)))) {
trypid++;
if (trypid >= pidchecked) {
PROC_UNLOCK(p2);
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goto retry;
}
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}
if (p2->p_pid > trypid && pidchecked > p2->p_pid)
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pidchecked = p2->p_pid;
if (p2->p_pgrp != NULL) {
if (p2->p_pgrp->pg_id > trypid &&
pidchecked > p2->p_pgrp->pg_id)
pidchecked = p2->p_pgrp->pg_id;
if (p2->p_session != NULL &&
p2->p_session->s_sid > trypid &&
pidchecked > p2->p_session->s_sid)
pidchecked = p2->p_session->s_sid;
}
PROC_UNLOCK(p2);
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}
if (!doingzomb) {
doingzomb = 1;
p2 = LIST_FIRST(&zombproc);
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goto again;
}
}
sx_sunlock(&proctree_lock);
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/*
* RFHIGHPID does not mess with the lastpid counter during boot.
*/
if (flags & RFHIGHPID)
pidchecked = 0;
else
lastpid = trypid;
p2 = newproc;
p2->p_state = PRS_NEW; /* protect against others */
p2->p_pid = trypid;
LIST_INSERT_HEAD(&allproc, p2, p_list);
LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash);
sx_xunlock(&allproc_lock);
/*
* Malloc things while we don't hold any locks.
*/
if (flags & RFSIGSHARE)
newsigacts = NULL;
else
newsigacts = sigacts_alloc();
/*
* Copy filedesc.
*/
if (flags & RFCFDG) {
FILEDESC_LOCK(td->td_proc->p_fd);
fd = fdinit(td->td_proc->p_fd);
FILEDESC_UNLOCK(td->td_proc->p_fd);
fdtol = NULL;
} else if (flags & RFFDG) {
FILEDESC_LOCK(p1->p_fd);
fd = fdcopy(td->td_proc->p_fd);
FILEDESC_UNLOCK(p1->p_fd);
fdtol = NULL;
} else {
fd = fdshare(p1->p_fd);
if (p1->p_fdtol == NULL)
p1->p_fdtol =
filedesc_to_leader_alloc(NULL,
NULL,
p1->p_leader);
if ((flags & RFTHREAD) != 0) {
/*
* Shared file descriptor table and
* shared process leaders.
*/
fdtol = p1->p_fdtol;
FILEDESC_LOCK(p1->p_fd);
fdtol->fdl_refcount++;
FILEDESC_UNLOCK(p1->p_fd);
} else {
/*
* Shared file descriptor table, and
* different process leaders
*/
fdtol = filedesc_to_leader_alloc(p1->p_fdtol,
p1->p_fd,
p2);
}
}
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/*
* Make a proc table entry for the new process.
* Start by zeroing the section of proc that is zero-initialized,
* then copy the section that is copied directly from the parent.
*/
td2 = FIRST_THREAD_IN_PROC(p2);
kg2 = FIRST_KSEGRP_IN_PROC(p2);
/* Allocate and switch to an alternate kstack if specified. */
if (pages != 0)
vm_thread_new_altkstack(td2, pages);
PROC_LOCK(p2);
PROC_LOCK(p1);
#define RANGEOF(type, start, end) (offsetof(type, end) - offsetof(type, start))
bzero(&p2->p_startzero,
(unsigned) RANGEOF(struct proc, p_startzero, p_endzero));
bzero(&td2->td_startzero,
(unsigned) RANGEOF(struct thread, td_startzero, td_endzero));
bzero(&kg2->kg_startzero,
(unsigned) RANGEOF(struct ksegrp, kg_startzero, kg_endzero));
bcopy(&p1->p_startcopy, &p2->p_startcopy,
(unsigned) RANGEOF(struct proc, p_startcopy, p_endcopy));
bcopy(&td->td_startcopy, &td2->td_startcopy,
(unsigned) RANGEOF(struct thread, td_startcopy, td_endcopy));
bcopy(&td->td_ksegrp->kg_startcopy, &kg2->kg_startcopy,
(unsigned) RANGEOF(struct ksegrp, kg_startcopy, kg_endcopy));
#undef RANGEOF
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td2->td_sigstk = td->td_sigstk;
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/*
* Duplicate sub-structures as needed.
* Increase reference counts on shared objects.
* The p_stats substruct is set in vm_forkproc.
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*/
p2->p_flag = 0;
if (p1->p_flag & P_PROFIL)
startprofclock(p2);
Change and clean the mutex lock interface. mtx_enter(lock, type) becomes: mtx_lock(lock) for sleep locks (MTX_DEF-initialized locks) mtx_lock_spin(lock) for spin locks (MTX_SPIN-initialized) similarily, for releasing a lock, we now have: mtx_unlock(lock) for MTX_DEF and mtx_unlock_spin(lock) for MTX_SPIN. We change the caller interface for the two different types of locks because the semantics are entirely different for each case, and this makes it explicitly clear and, at the same time, it rids us of the extra `type' argument. The enter->lock and exit->unlock change has been made with the idea that we're "locking data" and not "entering locked code" in mind. Further, remove all additional "flags" previously passed to the lock acquire/release routines with the exception of two: MTX_QUIET and MTX_NOSWITCH The functionality of these flags is preserved and they can be passed to the lock/unlock routines by calling the corresponding wrappers: mtx_{lock, unlock}_flags(lock, flag(s)) and mtx_{lock, unlock}_spin_flags(lock, flag(s)) for MTX_DEF and MTX_SPIN locks, respectively. Re-inline some lock acq/rel code; in the sleep lock case, we only inline the _obtain_lock()s in order to ensure that the inlined code fits into a cache line. In the spin lock case, we inline recursion and actually only perform a function call if we need to spin. This change has been made with the idea that we generally tend to avoid spin locks and that also the spin locks that we do have and are heavily used (i.e. sched_lock) do recurse, and therefore in an effort to reduce function call overhead for some architectures (such as alpha), we inline recursion for this case. Create a new malloc type for the witness code and retire from using the M_DEV type. The new type is called M_WITNESS and is only declared if WITNESS is enabled. Begin cleaning up some machdep/mutex.h code - specifically updated the "optimized" inlined code in alpha/mutex.h and wrote MTX_LOCK_SPIN and MTX_UNLOCK_SPIN asm macros for the i386/mutex.h as we presently need those. Finally, caught up to the interface changes in all sys code. Contributors: jake, jhb, jasone (in no particular order)
2001-02-09 06:11:45 +00:00
mtx_lock_spin(&sched_lock);
p2->p_sflag = PS_INMEM;
/*
* Allow the scheduler to adjust the priority of the child and
* parent while we hold the sched_lock.
*/
Refactor a bunch of scheduler code to give basically the same behaviour but with slightly cleaned up interfaces. The KSE structure has become the same as the "per thread scheduler private data" structure. In order to not make the diffs too great one is #defined as the other at this time. The KSE (or td_sched) structure is now allocated per thread and has no allocation code of its own. Concurrency for a KSEGRP is now kept track of via a simple pair of counters rather than using KSE structures as tokens. Since the KSE structure is different in each scheduler, kern_switch.c is now included at the end of each scheduler. Nothing outside the scheduler knows the contents of the KSE (aka td_sched) structure. The fields in the ksegrp structure that are to do with the scheduler's queueing mechanisms are now moved to the kg_sched structure. (per ksegrp scheduler private data structure). In other words how the scheduler queues and keeps track of threads is no-one's business except the scheduler's. This should allow people to write experimental schedulers with completely different internal structuring. A scheduler call sched_set_concurrency(kg, N) has been added that notifies teh scheduler that no more than N threads from that ksegrp should be allowed to be on concurrently scheduled. This is also used to enforce 'fainess' at this time so that a ksegrp with 10000 threads can not swamp a the run queue and force out a process with 1 thread, since the current code will not set the concurrency above NCPU, and both schedulers will not allow more than that many onto the system run queue at a time. Each scheduler should eventualy develop their own methods to do this now that they are effectively separated. Rejig libthr's kernel interface to follow the same code paths as linkse for scope system threads. This has slightly hurt libthr's performance but I will work to recover as much of it as I can. Thread exit code has been cleaned up greatly. exit and exec code now transitions a process back to 'standard non-threaded mode' before taking the next step. Reviewed by: scottl, peter MFC after: 1 week
2004-09-05 02:09:54 +00:00
sched_fork(td, td2);
Change and clean the mutex lock interface. mtx_enter(lock, type) becomes: mtx_lock(lock) for sleep locks (MTX_DEF-initialized locks) mtx_lock_spin(lock) for spin locks (MTX_SPIN-initialized) similarily, for releasing a lock, we now have: mtx_unlock(lock) for MTX_DEF and mtx_unlock_spin(lock) for MTX_SPIN. We change the caller interface for the two different types of locks because the semantics are entirely different for each case, and this makes it explicitly clear and, at the same time, it rids us of the extra `type' argument. The enter->lock and exit->unlock change has been made with the idea that we're "locking data" and not "entering locked code" in mind. Further, remove all additional "flags" previously passed to the lock acquire/release routines with the exception of two: MTX_QUIET and MTX_NOSWITCH The functionality of these flags is preserved and they can be passed to the lock/unlock routines by calling the corresponding wrappers: mtx_{lock, unlock}_flags(lock, flag(s)) and mtx_{lock, unlock}_spin_flags(lock, flag(s)) for MTX_DEF and MTX_SPIN locks, respectively. Re-inline some lock acq/rel code; in the sleep lock case, we only inline the _obtain_lock()s in order to ensure that the inlined code fits into a cache line. In the spin lock case, we inline recursion and actually only perform a function call if we need to spin. This change has been made with the idea that we generally tend to avoid spin locks and that also the spin locks that we do have and are heavily used (i.e. sched_lock) do recurse, and therefore in an effort to reduce function call overhead for some architectures (such as alpha), we inline recursion for this case. Create a new malloc type for the witness code and retire from using the M_DEV type. The new type is called M_WITNESS and is only declared if WITNESS is enabled. Begin cleaning up some machdep/mutex.h code - specifically updated the "optimized" inlined code in alpha/mutex.h and wrote MTX_LOCK_SPIN and MTX_UNLOCK_SPIN asm macros for the i386/mutex.h as we presently need those. Finally, caught up to the interface changes in all sys code. Contributors: jake, jhb, jasone (in no particular order)
2001-02-09 06:11:45 +00:00
mtx_unlock_spin(&sched_lock);
p2->p_ucred = crhold(td->td_ucred);
td2->td_ucred = crhold(p2->p_ucred); /* XXXKSE */
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pargs_hold(p2->p_args);
if (flags & RFSIGSHARE) {
p2->p_sigacts = sigacts_hold(p1->p_sigacts);
} else {
sigacts_copy(newsigacts, p1->p_sigacts);
p2->p_sigacts = newsigacts;
}
if (flags & RFLINUXTHPN)
p2->p_sigparent = SIGUSR1;
else
p2->p_sigparent = SIGCHLD;
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p2->p_textvp = p1->p_textvp;
p2->p_fd = fd;
p2->p_fdtol = fdtol;
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/*
* p_limit is copy-on-write. Bump its refcount.
1994-05-24 10:09:53 +00:00
*/
Locking for the per-process resource limits structure. - struct plimit includes a mutex to protect a reference count. The plimit structure is treated similarly to struct ucred in that is is always copy on write, so having a reference to a structure is sufficient to read from it without needing a further lock. - The proc lock protects the p_limit pointer and must be held while reading limits from a process to keep the limit structure from changing out from under you while reading from it. - Various global limits that are ints are not protected by a lock since int writes are atomic on all the archs we support and thus a lock wouldn't buy us anything. - All accesses to individual resource limits from a process are abstracted behind a simple lim_rlimit(), lim_max(), and lim_cur() API that return either an rlimit, or the current or max individual limit of the specified resource from a process. - dosetrlimit() was renamed to kern_setrlimit() to match existing style of other similar syscall helper functions. - The alpha OSF/1 compat layer no longer calls getrlimit() and setrlimit() (it didn't used the stackgap when it should have) but uses lim_rlimit() and kern_setrlimit() instead. - The svr4 compat no longer uses the stackgap for resource limits calls, but uses lim_rlimit() and kern_setrlimit() instead. - The ibcs2 compat no longer uses the stackgap for resource limits. It also no longer uses the stackgap for accessing sysctl's for the ibcs2_sysconf() syscall but uses kernel_sysctl() instead. As a result, ibcs2_sysconf() no longer needs Giant. - The p_rlimit macro no longer exists. Submitted by: mtm (mostly, I only did a few cleanups and catchups) Tested on: i386 Compiled on: alpha, amd64
2004-02-04 21:52:57 +00:00
p2->p_limit = lim_hold(p1->p_limit);
PROC_UNLOCK(p1);
PROC_UNLOCK(p2);
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/* Bump references to the text vnode (for procfs) */
if (p2->p_textvp)
vref(p2->p_textvp);
/*
* Set up linkage for kernel based threading.
*/
if ((flags & RFTHREAD) != 0) {
mtx_lock(&ppeers_lock);
p2->p_peers = p1->p_peers;
p1->p_peers = p2;
p2->p_leader = p1->p_leader;
mtx_unlock(&ppeers_lock);
PROC_LOCK(p1->p_leader);
if ((p1->p_leader->p_flag & P_WEXIT) != 0) {
PROC_UNLOCK(p1->p_leader);
/*
* The task leader is exiting, so process p1 is
* going to be killed shortly. Since p1 obviously
* isn't dead yet, we know that the leader is either
* sending SIGKILL's to all the processes in this
* task or is sleeping waiting for all the peers to
* exit. We let p1 complete the fork, but we need
* to go ahead and kill the new process p2 since
* the task leader may not get a chance to send
* SIGKILL to it. We leave it on the list so that
* the task leader will wait for this new process
* to commit suicide.
*/
PROC_LOCK(p2);
psignal(p2, SIGKILL);
PROC_UNLOCK(p2);
} else
PROC_UNLOCK(p1->p_leader);
} else {
p2->p_peers = NULL;
p2->p_leader = p2;
}
sx_xlock(&proctree_lock);
PGRP_LOCK(p1->p_pgrp);
PROC_LOCK(p2);
PROC_LOCK(p1);
/*
* Preserve some more flags in subprocess. P_PROFIL has already
* been preserved.
*/
p2->p_flag |= p1->p_flag & P_SUGID;
td2->td_pflags |= td->td_pflags & TDP_ALTSTACK;
SESS_LOCK(p1->p_session);
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if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
p2->p_flag |= P_CONTROLT;
SESS_UNLOCK(p1->p_session);
if (flags & RFPPWAIT)
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p2->p_flag |= P_PPWAIT;
p2->p_pgrp = p1->p_pgrp;
LIST_INSERT_AFTER(p1, p2, p_pglist);
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PGRP_UNLOCK(p1->p_pgrp);
LIST_INIT(&p2->p_children);
callout_init(&p2->p_itcallout, CALLOUT_MPSAFE);
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#ifdef KTRACE
/*
* Copy traceflag and tracefile if enabled.
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*/
mtx_lock(&ktrace_mtx);
KASSERT(p2->p_tracevp == NULL, ("new process has a ktrace vnode"));
if (p1->p_traceflag & KTRFAC_INHERIT) {
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p2->p_traceflag = p1->p_traceflag;
if ((p2->p_tracevp = p1->p_tracevp) != NULL) {
VREF(p2->p_tracevp);
KASSERT(p1->p_tracecred != NULL,
("ktrace vnode with no cred"));
p2->p_tracecred = crhold(p1->p_tracecred);
}
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}
mtx_unlock(&ktrace_mtx);
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#endif
/*
* If PF_FORK is set, the child process inherits the
* procfs ioctl flags from its parent.
*/
if (p1->p_pfsflags & PF_FORK) {
p2->p_stops = p1->p_stops;
p2->p_pfsflags = p1->p_pfsflags;
}
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/*
* This begins the section where we must prevent the parent
* from being swapped.
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*/
_PHOLD(p1);
PROC_UNLOCK(p1);
/*
* Attach the new process to its parent.
*
* If RFNOWAIT is set, the newly created process becomes a child
* of init. This effectively disassociates the child from the
* parent.
*/
if (flags & RFNOWAIT)
pptr = initproc;
else
pptr = p1;
p2->p_pptr = pptr;
LIST_INSERT_HEAD(&pptr->p_children, p2, p_sibling);
sx_xunlock(&proctree_lock);
/* Inform accounting that we have forked. */
p2->p_acflag = AFORK;
PROC_UNLOCK(p2);
/*
The biggie: Get rid of the UPAGES from the top of the per-process address space. (!) Have each process use the kernel stack and pcb in the kvm space. Since the stacks are at a different address, we cannot copy the stack at fork() and allow the child to return up through the function call tree to return to user mode - create a new execution context and have the new process begin executing from cpu_switch() and go to user mode directly. In theory this should speed up fork a bit. Context switch the tss_esp0 pointer in the common tss. This is a lot simpler since than swithching the gdt[GPROC0_SEL].sd.sd_base pointer to each process's tss since the esp0 pointer is a 32 bit pointer, and the sd_base setting is split into three different bit sections at non-aligned boundaries and requires a lot of twiddling to reset. The 8K of memory at the top of the process space is now empty, and unmapped (and unmappable, it's higher than VM_MAXUSER_ADDRESS). Simplity the pmap code to manage process contexts, we no longer have to double map the UPAGES, this simplifies and should measuably speed up fork(). The following parts came from John Dyson: Set PG_G on the UPAGES that are now in kernel context, and invalidate them when swapping them out. Move the upages object (upobj) from the vmspace to the proc structure. Now that the UPAGES (pcb and kernel stack) are out of user space, make rfork(..RFMEM..) do what was intended by sharing the vmspace entirely via reference counting rather than simply inheriting the mappings.
1997-04-07 07:16:06 +00:00
* Finish creating the child process. It will return via a different
* execution path later. (ie: directly into user mode)
*/
vm_forkproc(td, p2, td2, flags);
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if (flags == (RFFDG | RFPROC)) {
atomic_add_int(&cnt.v_forks, 1);
atomic_add_int(&cnt.v_forkpages, p2->p_vmspace->vm_dsize +
p2->p_vmspace->vm_ssize);
} else if (flags == (RFFDG | RFPROC | RFPPWAIT | RFMEM)) {
atomic_add_int(&cnt.v_vforks, 1);
atomic_add_int(&cnt.v_vforkpages, p2->p_vmspace->vm_dsize +
p2->p_vmspace->vm_ssize);
} else if (p1 == &proc0) {
atomic_add_int(&cnt.v_kthreads, 1);
atomic_add_int(&cnt.v_kthreadpages, p2->p_vmspace->vm_dsize +
p2->p_vmspace->vm_ssize);
} else {
atomic_add_int(&cnt.v_rforks, 1);
atomic_add_int(&cnt.v_rforkpages, p2->p_vmspace->vm_dsize +
p2->p_vmspace->vm_ssize);
}
/*
* Both processes are set up, now check if any loadable modules want
* to adjust anything.
* What if they have an error? XXX
*/
EVENTHANDLER_INVOKE(process_fork, p1, p2, flags);
/*
* Set the child start time and mark the process as being complete.
*/
microuptime(&p2->p_stats->p_start);
mtx_lock_spin(&sched_lock);
p2->p_state = PRS_NORMAL;
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/*
* If RFSTOPPED not requested, make child runnable and add to
* run queue.
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*/
if ((flags & RFSTOPPED) == 0) {
TD_SET_CAN_RUN(td2);
setrunqueue(td2, SRQ_BORING);
}
mtx_unlock_spin(&sched_lock);
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/*
* Now can be swapped.
*/
PROC_LOCK(p1);
_PRELE(p1);
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/*
* Tell any interested parties about the new process.
*/
KNOTE_LOCKED(&p1->p_klist, NOTE_FORK | p2->p_pid);
PROC_UNLOCK(p1);
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/*
* Preserve synchronization semantics of vfork. If waiting for
* child to exec or exit, set P_PPWAIT on child, and sleep on our
* proc (in case of exit).
*/
PROC_LOCK(p2);
while (p2->p_flag & P_PPWAIT)
msleep(p1, &p2->p_mtx, PWAIT, "ppwait", 0);
PROC_UNLOCK(p2);
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/*
* If other threads are waiting, let them continue now.
*/
if (p1->p_flag & P_HADTHREADS) {
PROC_LOCK(p1);
thread_single_end();
PROC_UNLOCK(p1);
}
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/*
* Return child proc pointer to parent.
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*/
*procp = p2;
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return (0);
fail:
sx_sunlock(&proctree_lock);
if (ppsratecheck(&lastfail, &curfail, 1))
printf("maxproc limit exceeded by uid %i, please see tuning(7) and login.conf(5).\n",
uid);
sx_xunlock(&allproc_lock);
#ifdef MAC
mac_destroy_proc(newproc);
#endif
uma_zfree(proc_zone, newproc);
if (p1->p_flag & P_HADTHREADS) {
PROC_LOCK(p1);
thread_single_end();
PROC_UNLOCK(p1);
}
tsleep(&forksleep, PUSER, "fork", hz / 2);
return (error);
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}
/*
* Handle the return of a child process from fork1(). This function
* is called from the MD fork_trampoline() entry point.
*/
void
fork_exit(callout, arg, frame)
void (*callout)(void *, struct trapframe *);
void *arg;
struct trapframe *frame;
{
struct proc *p;
struct thread *td;
/*
* Finish setting up thread glue so that it begins execution in a
* non-nested critical section with sched_lock held but not recursed.
*/
td = curthread;
p = td->td_proc;
td->td_oncpu = PCPU_GET(cpuid);
KASSERT(p->p_state == PRS_NORMAL, ("executing process is still new"));
sched_lock.mtx_lock = (uintptr_t)td;
mtx_assert(&sched_lock, MA_OWNED | MA_NOTRECURSED);
cpu_critical_fork_exit();
CTR4(KTR_PROC, "fork_exit: new thread %p (kse %p, pid %d, %s)",
Refactor a bunch of scheduler code to give basically the same behaviour but with slightly cleaned up interfaces. The KSE structure has become the same as the "per thread scheduler private data" structure. In order to not make the diffs too great one is #defined as the other at this time. The KSE (or td_sched) structure is now allocated per thread and has no allocation code of its own. Concurrency for a KSEGRP is now kept track of via a simple pair of counters rather than using KSE structures as tokens. Since the KSE structure is different in each scheduler, kern_switch.c is now included at the end of each scheduler. Nothing outside the scheduler knows the contents of the KSE (aka td_sched) structure. The fields in the ksegrp structure that are to do with the scheduler's queueing mechanisms are now moved to the kg_sched structure. (per ksegrp scheduler private data structure). In other words how the scheduler queues and keeps track of threads is no-one's business except the scheduler's. This should allow people to write experimental schedulers with completely different internal structuring. A scheduler call sched_set_concurrency(kg, N) has been added that notifies teh scheduler that no more than N threads from that ksegrp should be allowed to be on concurrently scheduled. This is also used to enforce 'fainess' at this time so that a ksegrp with 10000 threads can not swamp a the run queue and force out a process with 1 thread, since the current code will not set the concurrency above NCPU, and both schedulers will not allow more than that many onto the system run queue at a time. Each scheduler should eventualy develop their own methods to do this now that they are effectively separated. Rejig libthr's kernel interface to follow the same code paths as linkse for scope system threads. This has slightly hurt libthr's performance but I will work to recover as much of it as I can. Thread exit code has been cleaned up greatly. exit and exec code now transitions a process back to 'standard non-threaded mode' before taking the next step. Reviewed by: scottl, peter MFC after: 1 week
2004-09-05 02:09:54 +00:00
td, td->td_sched, p->p_pid, p->p_comm);
/*
* Processes normally resume in mi_switch() after being
* cpu_switch()'ed to, but when children start up they arrive here
* instead, so we must do much the same things as mi_switch() would.
*/
if ((td = PCPU_GET(deadthread))) {
PCPU_SET(deadthread, NULL);
thread_stash(td);
}
td = curthread;
mtx_unlock_spin(&sched_lock);
/*
* cpu_set_fork_handler intercepts this function call to
* have this call a non-return function to stay in kernel mode.
* initproc has its own fork handler, but it does return.
*/
KASSERT(callout != NULL, ("NULL callout in fork_exit"));
callout(arg, frame);
/*
* Check if a kernel thread misbehaved and returned from its main
* function.
*/
PROC_LOCK(p);
if (p->p_flag & P_KTHREAD) {
PROC_UNLOCK(p);
printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n",
p->p_comm, p->p_pid);
kthread_exit(0);
}
PROC_UNLOCK(p);
mtx_assert(&Giant, MA_NOTOWNED);
}
/*
* Simplified back end of syscall(), used when returning from fork()
* directly into user mode. Giant is not held on entry, and must not
* be held on return. This function is passed in to fork_exit() as the
* first parameter and is called when returning to a new userland process.
*/
void
fork_return(td, frame)
struct thread *td;
struct trapframe *frame;
{
userret(td, frame, 0);
#ifdef KTRACE
if (KTRPOINT(td, KTR_SYSRET))
ktrsysret(SYS_fork, 0, 0);
#endif
mtx_assert(&Giant, MA_NOTOWNED);
}