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Turn MAXPTSDEVS into a sysctl tunable.

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This allows users to increase the maximum amount of pseudo-terminals
without changing any source code. Users must increase UT_LINESIZE before
attempting to increase kern.pts_maxdev.
This commit is contained in:
Ed Schouten 2009-04-25 10:05:55 +00:00
parent 016a3c93b2
commit ccfd3aab30
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=191484
2 changed files with 37 additions and 2 deletions
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20
share/man/man4/pts.4
View File

@ -156,6 +156,26 @@ though
.It Pa /dev/pts/[num]
Pseudo-terminal slave devices.
.El
.Sh SYSCTL VARIABLES
The following
.Xr sysctl 8
variables can be used to modify or monitor
.Nm
behavior.
.Bl -tag -width indent
.It Va kern.pts_maxdev
Highest pseudo-terminal unit number to be allocated.
Because
.Xr utmp 5
is restricted to an 8-byte line name size,
.Nm
will not create any pseudo-terminals with a unit number above 999 by
default.
After increasing
.Dv UT_LINESIZE ,
this variable can be changed to allow more than 1000 pseudo-terminals to
be allocated simultaneously.
.El
.Sh DIAGNOSTICS
None.
.Sh SEE ALSO

19
sys/kern/tty_pts.c
View File

@ -50,6 +50,7 @@ __FBSDID("$FreeBSD$");
#include <sys/filedesc.h>
#include <sys/filio.h>
#include <sys/kernel.h>
#include <sys/limits.h>
#include <sys/malloc.h>
#include <sys/poll.h>
#include <sys/proc.h>
@ -58,6 +59,7 @@ __FBSDID("$FreeBSD$");
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/syscallsubr.h>
#include <sys/sysctl.h>
#include <sys/sysent.h>
#include <sys/sysproto.h>
#include <sys/systm.h>
@ -66,8 +68,16 @@ __FBSDID("$FreeBSD$");
#include <machine/stdarg.h>
/*
* Our utmp(5) format is limited to 8-byte TTY line names. This means
* we can at most allocate 1000 pseudo-terminals ("pts/999"). Allow
* users to increase this number, assuming they have manually increased
* UT_LINESIZE.
*/
static struct unrhdr *pts_pool;
#define MAXPTSDEVS 999
static unsigned int pts_maxdev = 999;
SYSCTL_UINT(_kern, OID_AUTO, pts_maxdev, CTLFLAG_RW, &pts_maxdev, 0,
"Maximum amount of pts(4) pseudo-terminals");
static MALLOC_DEFINE(M_PTS, "pts", "pseudo tty device");
@ -716,6 +726,11 @@ pts_alloc(int fflags, struct thread *td, struct file *fp)
chgptscnt(uid, -1, 0);
return (EAGAIN);
}
if (unit > pts_maxdev) {
free_unr(pts_pool, unit);
chgptscnt(uid, -1, 0);
return (EAGAIN);
}
/* Allocate TTY and softc. */
psc = malloc(sizeof(struct pts_softc), M_PTS, M_WAITOK|M_ZERO);
@ -829,7 +844,7 @@ static void
pts_init(void *unused)
{
pts_pool = new_unrhdr(0, MAXPTSDEVS, NULL);
pts_pool = new_unrhdr(0, INT_MAX, NULL);
#if defined(PTS_COMPAT) || defined(PTS_LINUX)
make_dev(&ptmx_cdevsw, 0, UID_ROOT, GID_WHEEL, 0666, "ptmx");
#endif /* PTS_COMPAT || PTS_LINUX */