that the tty is dequeued from 'tty_list' only the first time.
The panic below was seen when a revoke(2) was issued on an nmdm device.
In this case there was also a thread that was blocked on a read(2) on the
device. The revoke(2) woke up the blocked thread which would typically
return an error to userspace. In this case the reader also held the last
reference on the file descriptor so fdrop() ended up calling tty_rel_free()
via ttydev_close().
tty_rel_free() then tried to dequeue 'tp' again which led to the panic.
panic: Bad link elm 0xfffff80042602400 prev->next != elm
cpuid = 1
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe00f9c90460
kdb_backtrace() at kdb_backtrace+0x39/frame 0xfffffe00f9c90510
vpanic() at vpanic+0x189/frame 0xfffffe00f9c90590
panic() at panic+0x43/frame 0xfffffe00f9c905f0
tty_rel_free() at tty_rel_free+0x29b/frame 0xfffffe00f9c90640
ttydev_close() at ttydev_close+0x1f9/frame 0xfffffe00f9c90690
devfs_close() at devfs_close+0x298/frame 0xfffffe00f9c90720
VOP_CLOSE_APV() at VOP_CLOSE_APV+0x13c/frame 0xfffffe00f9c90770
vn_close() at vn_close+0x194/frame 0xfffffe00f9c90810
vn_closefile() at vn_closefile+0x48/frame 0xfffffe00f9c90890
devfs_close_f() at devfs_close_f+0x2c/frame 0xfffffe00f9c908c0
_fdrop() at _fdrop+0x29/frame 0xfffffe00f9c908e0
sys_read() at sys_read+0x63/frame 0xfffffe00f9c90980
amd64_syscall() at amd64_syscall+0x2b3/frame 0xfffffe00f9c90ab0
Xfast_syscall() at Xfast_syscall+0xfb/frame 0xfffffe00f9c90ab0
--- syscall (3, FreeBSD ELF64, sys_read), rip = 0x800b78d8a, rsp = 0x7fffffbfdaf8, rbp = 0x7fffffbfdb30 ---
CR: https://reviews.freebsd.org/D851
Reviewed by: glebius, ed
Reported by: Leon Dang
Sponsored by: Nahanni Systems
MFC after: 1 week
is the indication that draining got interrupted due to a revoke(2) and
that tty_drain() is to be called again for draining to complete. If the
device is flagged as gone, then waiting/draining is not possible. Only
return ERESTART when waiting is still possible.
Obtained from: Juniper Networks, Inc.
further refinement is required as some device drivers intended to be
portable over FreeBSD versions rely on __FreeBSD_version to decide whether
to include capability.h.
MFC after: 3 weeks
to fail and return error.
- Use make_dev_p() in tty_makedevf() instead of make_dev_cred().
- Always pass MAKEDEV_CHECKNAME flag.
- Optionally pass MAKEDEV_REF flag.
- Provide macro for compatibility with old API.
This fixes races with simultaneous creation and desctruction of
ttys, and makes it possible to call tty_makedevf() from device
cloners.
A race in tty_watermarks() still exist, since the latter drops
lock for M_WAITOK allocation. This will be addressed in separate
commit.
Reviewed by: kib
Sponsored by: Nginx, Inc.
the TTY. In such a case, ttydev_close() is called multiple times and
each time, t_revokecnt is incremented and cv_broadcast() is called for
both the t_outwait and t_inwait condition variables.
Let's say revoke(2) comes in first and gets to call tty_drain() from
ttydev_leave(). Let's say that the revoke comes from init(8) as the
result of running "shutdown -r now". Since shutdown prints various
messages to the console before announing that the machine will reboot
immediately, let's also say that the output queue is not empty and
that tty_drain() has something to do. Let's assume this all happens
on a 9600 baud serial console, so it takes a time to drain.
The shutdown command will exit(2) and as such will end up closing
stdout. Let's say this close will come in second, bump t_revokecnt
and call tty_wakeup(). This has tty_wait() return prematurely and
the next thing that will happen is that the thread doing revoke(2)
will flush the TTY. Since the drain wasn't complete, the flush will
effectively drop whatever is left in t_outq.
This change takes into account that tty_drain() will return ERESTART
due to the fact that t_revokecnt was bumped and in that case simply
call tty_drain() again. The thread in question is already performing
the close so it can safely finish draining the TTY before destroying
the TTY structure.
Now all messages from shutdown will be printed on the serial console.
Obtained from: Juniper Networks, Inc.
in the future in a backward compatible (API and ABI) way.
The cap_rights_t represents capability rights. We used to use one bit to
represent one right, but we are running out of spare bits. Currently the new
structure provides place for 114 rights (so 50 more than the previous
cap_rights_t), but it is possible to grow the structure to hold at least 285
rights, although we can make it even larger if 285 rights won't be enough.
The structure definition looks like this:
struct cap_rights {
uint64_t cr_rights[CAP_RIGHTS_VERSION + 2];
};
The initial CAP_RIGHTS_VERSION is 0.
The top two bits in the first element of the cr_rights[] array contain total
number of elements in the array - 2. This means if those two bits are equal to
0, we have 2 array elements.
The top two bits in all remaining array elements should be 0.
The next five bits in all array elements contain array index. Only one bit is
used and bit position in this five-bits range defines array index. This means
there can be at most five array elements in the future.
To define new right the CAPRIGHT() macro must be used. The macro takes two
arguments - an array index and a bit to set, eg.
#define CAP_PDKILL CAPRIGHT(1, 0x0000000000000800ULL)
We still support aliases that combine few rights, but the rights have to belong
to the same array element, eg:
#define CAP_LOOKUP CAPRIGHT(0, 0x0000000000000400ULL)
#define CAP_FCHMOD CAPRIGHT(0, 0x0000000000002000ULL)
#define CAP_FCHMODAT (CAP_FCHMOD | CAP_LOOKUP)
There is new API to manage the new cap_rights_t structure:
cap_rights_t *cap_rights_init(cap_rights_t *rights, ...);
void cap_rights_set(cap_rights_t *rights, ...);
void cap_rights_clear(cap_rights_t *rights, ...);
bool cap_rights_is_set(const cap_rights_t *rights, ...);
bool cap_rights_is_valid(const cap_rights_t *rights);
void cap_rights_merge(cap_rights_t *dst, const cap_rights_t *src);
void cap_rights_remove(cap_rights_t *dst, const cap_rights_t *src);
bool cap_rights_contains(const cap_rights_t *big, const cap_rights_t *little);
Capability rights to the cap_rights_init(), cap_rights_set(),
cap_rights_clear() and cap_rights_is_set() functions are provided by
separating them with commas, eg:
cap_rights_t rights;
cap_rights_init(&rights, CAP_READ, CAP_WRITE, CAP_FSTAT);
There is no need to terminate the list of rights, as those functions are
actually macros that take care of the termination, eg:
#define cap_rights_set(rights, ...) \
__cap_rights_set((rights), __VA_ARGS__, 0ULL)
void __cap_rights_set(cap_rights_t *rights, ...);
Thanks to using one bit as an array index we can assert in those functions that
there are no two rights belonging to different array elements provided
together. For example this is illegal and will be detected, because CAP_LOOKUP
belongs to element 0 and CAP_PDKILL to element 1:
cap_rights_init(&rights, CAP_LOOKUP | CAP_PDKILL);
Providing several rights that belongs to the same array's element this way is
correct, but is not advised. It should only be used for aliases definition.
This commit also breaks compatibility with some existing Capsicum system calls,
but I see no other way to do that. This should be fine as Capsicum is still
experimental and this change is not going to 9.x.
Sponsored by: The FreeBSD Foundation
- Capability is no longer separate descriptor type. Now every descriptor
has set of its own capability rights.
- The cap_new(2) system call is left, but it is no longer documented and
should not be used in new code.
- The new syscall cap_rights_limit(2) should be used instead of
cap_new(2), which limits capability rights of the given descriptor
without creating a new one.
- The cap_getrights(2) syscall is renamed to cap_rights_get(2).
- If CAP_IOCTL capability right is present we can further reduce allowed
ioctls list with the new cap_ioctls_limit(2) syscall. List of allowed
ioctls can be retrived with cap_ioctls_get(2) syscall.
- If CAP_FCNTL capability right is present we can further reduce fcntls
that can be used with the new cap_fcntls_limit(2) syscall and retrive
them with cap_fcntls_get(2).
- To support ioctl and fcntl white-listing the filedesc structure was
heavly modified.
- The audit subsystem, kdump and procstat tools were updated to
recognize new syscalls.
- Capability rights were revised and eventhough I tried hard to provide
backward API and ABI compatibility there are some incompatible changes
that are described in detail below:
CAP_CREATE old behaviour:
- Allow for openat(2)+O_CREAT.
- Allow for linkat(2).
- Allow for symlinkat(2).
CAP_CREATE new behaviour:
- Allow for openat(2)+O_CREAT.
Added CAP_LINKAT:
- Allow for linkat(2). ABI: Reuses CAP_RMDIR bit.
- Allow to be target for renameat(2).
Added CAP_SYMLINKAT:
- Allow for symlinkat(2).
Removed CAP_DELETE. Old behaviour:
- Allow for unlinkat(2) when removing non-directory object.
- Allow to be source for renameat(2).
Removed CAP_RMDIR. Old behaviour:
- Allow for unlinkat(2) when removing directory.
Added CAP_RENAMEAT:
- Required for source directory for the renameat(2) syscall.
Added CAP_UNLINKAT (effectively it replaces CAP_DELETE and CAP_RMDIR):
- Allow for unlinkat(2) on any object.
- Required if target of renameat(2) exists and will be removed by this
call.
Removed CAP_MAPEXEC.
CAP_MMAP old behaviour:
- Allow for mmap(2) with any combination of PROT_NONE, PROT_READ and
PROT_WRITE.
CAP_MMAP new behaviour:
- Allow for mmap(2)+PROT_NONE.
Added CAP_MMAP_R:
- Allow for mmap(PROT_READ).
Added CAP_MMAP_W:
- Allow for mmap(PROT_WRITE).
Added CAP_MMAP_X:
- Allow for mmap(PROT_EXEC).
Added CAP_MMAP_RW:
- Allow for mmap(PROT_READ | PROT_WRITE).
Added CAP_MMAP_RX:
- Allow for mmap(PROT_READ | PROT_EXEC).
Added CAP_MMAP_WX:
- Allow for mmap(PROT_WRITE | PROT_EXEC).
Added CAP_MMAP_RWX:
- Allow for mmap(PROT_READ | PROT_WRITE | PROT_EXEC).
Renamed CAP_MKDIR to CAP_MKDIRAT.
Renamed CAP_MKFIFO to CAP_MKFIFOAT.
Renamed CAP_MKNODE to CAP_MKNODEAT.
CAP_READ old behaviour:
- Allow pread(2).
- Disallow read(2), readv(2) (if there is no CAP_SEEK).
CAP_READ new behaviour:
- Allow read(2), readv(2).
- Disallow pread(2) (CAP_SEEK was also required).
CAP_WRITE old behaviour:
- Allow pwrite(2).
- Disallow write(2), writev(2) (if there is no CAP_SEEK).
CAP_WRITE new behaviour:
- Allow write(2), writev(2).
- Disallow pwrite(2) (CAP_SEEK was also required).
Added convinient defines:
#define CAP_PREAD (CAP_SEEK | CAP_READ)
#define CAP_PWRITE (CAP_SEEK | CAP_WRITE)
#define CAP_MMAP_R (CAP_MMAP | CAP_SEEK | CAP_READ)
#define CAP_MMAP_W (CAP_MMAP | CAP_SEEK | CAP_WRITE)
#define CAP_MMAP_X (CAP_MMAP | CAP_SEEK | 0x0000000000000008ULL)
#define CAP_MMAP_RW (CAP_MMAP_R | CAP_MMAP_W)
#define CAP_MMAP_RX (CAP_MMAP_R | CAP_MMAP_X)
#define CAP_MMAP_WX (CAP_MMAP_W | CAP_MMAP_X)
#define CAP_MMAP_RWX (CAP_MMAP_R | CAP_MMAP_W | CAP_MMAP_X)
#define CAP_RECV CAP_READ
#define CAP_SEND CAP_WRITE
#define CAP_SOCK_CLIENT \
(CAP_CONNECT | CAP_GETPEERNAME | CAP_GETSOCKNAME | CAP_GETSOCKOPT | \
CAP_PEELOFF | CAP_RECV | CAP_SEND | CAP_SETSOCKOPT | CAP_SHUTDOWN)
#define CAP_SOCK_SERVER \
(CAP_ACCEPT | CAP_BIND | CAP_GETPEERNAME | CAP_GETSOCKNAME | \
CAP_GETSOCKOPT | CAP_LISTEN | CAP_PEELOFF | CAP_RECV | CAP_SEND | \
CAP_SETSOCKOPT | CAP_SHUTDOWN)
Added defines for backward API compatibility:
#define CAP_MAPEXEC CAP_MMAP_X
#define CAP_DELETE CAP_UNLINKAT
#define CAP_MKDIR CAP_MKDIRAT
#define CAP_RMDIR CAP_UNLINKAT
#define CAP_MKFIFO CAP_MKFIFOAT
#define CAP_MKNOD CAP_MKNODAT
#define CAP_SOCK_ALL (CAP_SOCK_CLIENT | CAP_SOCK_SERVER)
Sponsored by: The FreeBSD Foundation
Reviewed by: Christoph Mallon <christoph.mallon@gmx.de>
Many aspects discussed with: rwatson, benl, jonathan
ABI compatibility discussed with: kib
In the old TTY layer, SIGTTIN was correctly handled like this:
while (data should be read) {
send SIGTTIN if not foreground process group
read data
}
In the new TTY layer, however, this behaviour was changed, based on a
false interpretation of the standard:
send SIGTTIN if not foreground process group
while (data should be read) {
read data
}
Correct this by pushing tty_wait_background() into the ttydisc_read_*()
functions.
Reported by: koitsu
PR: kern/173010
MFC after: 2 weeks
dev = make_dev_cred();
dev->si_drv1 = tp;
leaves a small window where the newly created device may be opened
and si_drv1 is NULL.
As this is a vary rare situation, using a lock to close the window
seems overkill. Instead just wait for the assignment of si_drv1.
Suggested by: kib
MFC after: 1 week
Uftdi(4) examines (c_iflag & (IXON|IXOFF)) to control hw XON-XOFF support.
This is obviously no good, if changes to those bits are not communicated
down the stack.
patch modifies makesyscalls.sh to prefix all of the non-compatibility
calls (e.g. not linux_, freebsd32_) with sys_ and updates the kernel
entry points and all places in the code that use them. It also
fixes an additional name space collision between the kernel function
psignal and the libc function of the same name by renaming the kernel
psignal kern_psignal(). By introducing this change now we will ease future
MFCs that change syscalls.
Reviewed by: rwatson
Approved by: re (bz)
In revision 223722 we introduced support for driver ioctls on init/lock
state devices. Unfortunately the call to ttydevsw_cioctl() clobbers the
value of the error variable, meaning that in many cases ioctl() will now
return ENOTTY, even though the ioctl() was processed properly.
Reported by: Boris Samorodov <bsam ipt ru>
Patch by: jilles@
Approved by: re@ (kib@)
If a selinfo object is recorded (via selrecord()) and then it is
quickly destroyed, with the waiters missing the opportunity to awake,
at the next iteration they will find the selinfo object destroyed,
causing a PF#.
That happens because the selinfo interface has no way to drain the
waiters before to destroy the registered selinfo object. Also this
race is quite rare to get in practice, because it would require a
selrecord(), a poll request by another thread and a quick destruction
of the selrecord()'ed selinfo object.
Fix this by adding the seldrain() routine which should be called
before to destroy the selinfo objects (in order to avoid such case),
and fix the present cases where it might have already been called.
Sometimes, the context is safe enough to prevent this type of race,
like it happens in device drivers which installs selinfo objects on
poll callbacks. There, the destruction of the selinfo object happens
at driver detach time, when all the filedescriptors should be already
closed, thus there cannot be a race.
For this case, mfi(4) device driver can be set as an example, as it
implements a full correct logic for preventing this from happening.
Sponsored by: Sandvine Incorporated
Reported by: rstone
Tested by: pluknet
Reviewed by: jhb, kib
Approved by: re (bz)
MFC after: 3 weeks
kernel for FreeBSD 9.0:
Add a new capability mask argument to fget(9) and friends, allowing system
call code to declare what capabilities are required when an integer file
descriptor is converted into an in-kernel struct file *. With options
CAPABILITIES compiled into the kernel, this enforces capability
protection; without, this change is effectively a no-op.
Some cases require special handling, such as mmap(2), which must preserve
information about the maximum rights at the time of mapping in the memory
map so that they can later be enforced in mprotect(2) -- this is done by
narrowing the rights in the existing max_protection field used for similar
purposes with file permissions.
In namei(9), we assert that the code is not reached from within capability
mode, as we're not yet ready to enforce namespace capabilities there.
This will follow in a later commit.
Update two capability names: CAP_EVENT and CAP_KEVENT become
CAP_POST_KEVENT and CAP_POLL_KEVENT to more accurately indicate what they
represent.
Approved by: re (bz)
Submitted by: jonathan
Sponsored by: Google Inc
The cioctl() hook can be used by drivers to add ioctls to the *.init and
*.lock devices. This commit breaks the ttydevsw ABI, since this
structure didn't provide any padding. To prevent ABI breakage in the
future, add a tsw_spare.
Submitted by: Peter Jeremy <peter jeremy alcatel lucent com>
Obtained from: kern/152254 (slightly modified)
Instead of adding custom checks to wait for DCD on open(), just modify
the termios structure to set CLOCAL. This means SIGHUP is no longer
generated when losing DCD as well.
Reviewed by: kib@
MFC after: 1 week
This makes /dev/console more fail-safe and prevents a potential console
lock-up during boot.
Discussed on: stable@
Tested by: koitsu@
MFC after: 1 week
cdev will never be destroyed. Propagate the flag to devfs vnodes as
VV_ETERNVALDEV. Use the flags to avoid acquiring devmtx and taking a
thread reference on such nodes.
In collaboration with: pho
MFC after: 1 month
There are special cases where tty_rel_free() can be called twice in a
row, namely when closing and revoking the TTY at the same moment. Only
call destroy_dev_sched_cb() once.
Reported by: Jeremie Le Hen
MFC after: 1 week
It looks like I didn't implement this when I imported MPSAFE TTY.
Applications like mail(1) still use this. I think it's conceptually bad.
Tested by: Pete French <petefrench ticketswitch com>
MFC after: 2 weeks
This replaces d_mmap() with the d_mmap2() implementation and also
changes the type of offset to vm_ooffset_t.
Purge d_mmap2().
All driver modules will need to be rebuilt since D_VERSION is also
bumped.
Reviewed by: jhb@
MFC after: Not in this lifetime...
When the termios CREAD flag is not set, it makes little sense to
allocate an input buffer. Just set the size to 0 in this case to reduce
memory footprint.
Disallow CREAD to be disabled for pseudo-devices to prevent
foot-shooting.
to fail due to lack of resources to queue siginfo. Add KSI_SIGQ flag
that allows sigqueue_add() to fail while trying to allocate memory for
new siginfo. When the flag is not set, behaviour is the same as for
KSI_TRAP: if memory cannot be allocated, set bit in sq_kill. KSI_TRAP is
kept to preserve KBI.
Add SI_KERNEL si_code, to be used in siginfo.si_code when signal is
generated by kernel. Deliver siginfo when signal is generated by kill(2)
family of syscalls (SI_USER with properly filled si_uid and si_pid), or
by kernel (SI_KERNEL, mostly job control or SIGIO). Since KSI_SIGQ flag
is not set for the ksi, low memory condition cause old behaviour.
Keep psignal(9) KBI intact, but modify it to generate SI_KERNEL
si_code. Pgsignal(9) and gsignal(9) now take ksi explicitely. Add
pksignal(9) that behaves like psignal but takes ksi, and ddb kill
command implemented as pksignal(..., ksi = NULL) to not do allocation
while in debugger.
While there, remove some register specifiers and use ANSI C prototypes.
Reviewed by: davidxu
MFC after: 1 month
Now that buffers are deallocated lazily, we should not use
tty*q_getsize() to obtain the buffer size to calculate the low
watermarks. Doing this may cause the watermark to be placed outside the
typical buffer size.
This caused some regressions after my previous commit to the TTY code,
which allows pseudo-devices to resize the buffers as well.
Reported by: yongari, dougb
MFC after: 1 week
Devices that don't implement param() (which means they don't support
hardware parameters such as flow control, baud rate) hardcode the baud
rate to TTYDEF_SPEED. This means the buffer size cannot be configured,
which is a little inconvenient when using canonical mode with big lines
of input, etc.
Make it adjustable, but do clamp it between B50 and B115200 to prevent
awkward buffer sizes. Remove the baud rate assignment from
/etc/gettytab. Trust the kernel to fill in a proper value.
Reported by: Mikolaj Golub <to my trociny gmail com>
MFC after: 1 month
It turned out I did add the code to use the init state devices to set
the termios structure when opening the device, but it seems I totally
forgot to add the bits required to force the actual locking of flags
through the lock state devices.
Reported by: ru
MFC after: 1 week (to be discussed)
As pointed out, POLLHUP should be generated, even if it hasn't been
specified on input. It is also not allowed to return both POLLOUT and
POLLHUP at the same time.
Reported by: jilles
Approved by: re (kib)
The advantage of using a separate condvar is that we can just use
cv_signal(9) instead of cv_broadcast(9). It makes no sense to wake up
multiple threads. It also makes the TTY code easier to understand.
t_dcdwait sounds totally unrelated.
I suspect the usage of bgwait causes a lot of spurious wakeups when
threads are blocked in the background, because they will be woken up
each time a write() call is performed.
Also wakeup dcdwait when the TTY is abandoned.
Now that we start to use credentials on character devices more often
(because of MPSAFE TTY), move the prison-checks that are in place in the
TTY code into devfs.
Instead of strictly comparing the prisons, use the more common
prison_check() function to compare credentials. This means that
pseudo-terminals are only visible in devfs by processes within the same
jail and parent jails.
Even though regular users in parent jails can now interact with
pseudo-terminals from child jails, this seems to be the right approach.
These processes are also capable of interacting with the jailed
processes anyway, through signals for example.
Reviewed by: kib, rwatson (older version)
The code that was in place in exit1() was mainly based on code from the
old TTY layer. The main reason behind this, was because at one moment I
ran a system that had two TTY layers in place at the same time. It is
now sufficient to do the following:
- Remove references from the session structure to the TTY vnode and the
session leader.
- If we have a controlling TTY and the session used by the TTY is equal
to our session, send the SIGHUP.
- If we have a vnode to the controlling TTY which has not been revoked,
revoke it.
While there, change sys/kern/tty.c to use s_ttyp in the comparison
instead of s_ttyvp. It should not make any difference, because s_ttyvp
can only become null when the session leader already left, but it's
nicer to compare against the proper value.
Right now the only way to make tcsetsid(3)/TIOCSCTTY work, is by
ensuring the session leader is dead. This means that an application that
catches SIGHUPs and performs a sleep prevents us from assigning a new
session leader.
Change the code to make it work on revoked TTYs as well. This allows us
to change init(8) to make the shutdown script run in a more clean
environment.
Because our rc scripts also open the /etc/ttyv* nodes, it revokes the
console, preventing startup messages from being displayed.
I really have to think about this. Maybe we should just give the console
its own TTY and let it build on top of other TTYs. I'm still not sure
what to do with input handling there.
Even though I thought I fixed the staircase issue (and I was no longer
able to reproduce it), I got some reports of the issue still being
there. It turns out the staircase effect still occurred when
/dev/console was kept open while killing the getty on the same TTY
(ttyv0).
For some reason I can't figure out how the old TTY code dealt with that,
so I assume the issue has always been there. I only exposed it more by
merging consolectl with ttyv0, which means that the issue was present,
even on systems without a serial console.
I'm now marking the console device as being closed when closing the
regular TTY device node. This means that when the getty shuts down,
init(8) will open /dev/console, which means the termios attributes will
always be reset in this case.
vnode interlock to protect the knote fields [1]. The locking assumes
that shared vnode lock is held, thus we get exclusive access to knote
either by exclusive vnode lock protection, or by shared vnode lock +
vnode interlock.
Do not use kl_locked() method to assert either lock ownership or the
fact that curthread does not own the lock. For shared locks, ownership
is not recorded, e.g. VOP_ISLOCKED can return LK_SHARED for the shared
lock not owned by curthread, causing false positives in kqueue subsystem
assertions about knlist lock.
Remove kl_locked method from knlist lock vector, and add two separate
assertion methods kl_assert_locked and kl_assert_unlocked, that are
supposed to use proper asserts. Change knlist_init accordingly.
Add convenience function knlist_init_mtx to reduce number of arguments
for typical knlist initialization.
Submitted by: jhb [1]
Noted by: jhb [2]
Reviewed by: jhb
Tested by: rnoland
I don't want people to override the mutex when allocating a TTY. It has
to be there, to keep drivers like syscons happy. So I'm creating a
tty_alloc_mutex() which can be used in those cases. tty_alloc_mutex()
should eventually be removed.
The advantage of this approach, is that we can just remove a function,
without breaking the regular API in the future.
In the original MPSAFE TTY code, I changed the behaviour by returning
EBUSY. I thought this made more sense, because it's basically a race to
see who gets the TTY first.
It turns out this is not a good change, because it also causes EBUSY to
be returned when another process is closing the TTY. This can happen
during startup, when /etc/rc (or one of its children) is still busy
draining its data and /sbin/init is attempting to open the TTY to spawn
a getty.
Reported by: bz
Tested by: bz
fget_unlocked().
- Save old file descriptor tables created on expansion until
the entire descriptor table is freed so that pointers may be
followed without regard for expanders.
- Mark the file zone as NOFREE so we may attempt to reference
potentially freed files.
- Convert several fget_locked() users to fget_unlocked(). This
requires us to manage reference counts explicitly but reduces
locking overhead in the common case.
