A later change, currently being iterated on in D24459, will in-fact change
the lock type to an sx so that TTY drivers can sleep on it if they need to.
Committing this ahead of time to make the review in question a little more
palatable.
tty_lock_assert() is unfortunately still needed for now in two places to
make sure that the tty lock has not been recursed upon, for those scenarios
where it's supplied by the TTY driver and possibly a mutex that is allowed
to recurse.
Suggested by: markj
After r355784 the td_oncpu field is no longer synchronized by the thread
lock, so the stack capture interrupt cannot be delievered precisely.
Fix this using a loop which drops the thread lock and restarts if the
wrong thread was sampled from the stack capture interrupt handler.
Change the implementation to use a regular interrupt instead of an NMI.
Now that we drop the thread lock, there is no advantage to the latter.
Simplify the KPIs. Remove stack_save_td_running() and add a return
value to stack_save_td(). On platforms that do not support stack
capture of running threads, stack_save_td() returns EOPNOTSUPP. If the
target thread is running in user mode, stack_save_td() returns EBUSY.
Reviewed by: kib
Reported by: mjg, pho
Tested by: pho
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D23355
We by definition cannot trace the stack of such a thread. Also remove a
redundant stack_zero() call in the SIGINFO handler, the stack structure
is cleared by the MD stack_capture().
Sponsored by: The FreeBSD Foundation
Different compilation units may otherwise get a different view of the
layout of struct tty depending on whether they include opt_printf.h.
This caused a blowup in the number of types defined in the kernel's
CTF file after r339468; thanks to dim@ for bisecting down to that
revision.
PR: 232675
Reported by: dim
Reviewed by: cem (previous version)
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D17877
It is often useful for developers and administrators to determine a running
thread's stack for debugging purposes. With this feature, using ^T will
print that information
For now, the feature is disabled by default. Enable with sysctl
kern.tty_info_kstacks=1.
Discussed with: markj
Reviewed by: oshogbo
Relnotes: yes
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D17621
Mainly focus on files that use BSD 3-Clause license.
The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.
Special thanks to Wind River for providing access to "The Duke of
Highlander" tool: an older (2014) run over FreeBSD tree was useful as a
starting point.
This makes siginfo output look a lot better when pressing it the first
time when in sh(1), for example:
$ load: 0.00 cmd: sh 1945 [ttyin] 3.94r 0.00u 0.00s 0% 1960k
load: 0.00 cmd: sh 1945 [ttyin] 4.19r 0.00u 0.00s 0% 1960k
will now become:
$
load: 0.00 cmd: sh 1945 [ttyin] 3.94r 0.00u 0.00s 0% 1960k
load: 0.00 cmd: sh 1945 [ttyin] 4.19r 0.00u 0.00s 0% 1960k
- Only pick up PROC_LOCK once, which means we can drop the PGRP_LOCK
right after picking up PROC_LOCK for the first time.
- Print the process real time, making it consistent with tools like
time(1).
- Use `p' and `td' to reference the process/thread we are going to
print. Only use pick-variables inside the loops. We already did this
for the threads, but not the processes.
kern_time.c:
- Unused variable `p'.
kern_thr.c:
- Variable `error' is always caught immediately, so no reason to
initialize it. There is no way that error != 0 at the end of
create_thread().
kern_sig.c:
- Unused variable `code'.
kern_synch.c:
- `rval' is always assigned in all different cases.
kern_rwlock.c:
- `v' is always overwritten with RW_UNLOCKED further on.
kern_malloc.c:
- `size' is always initialized with the proper value before being used.
kern_exit.c:
- `error' is always caught and returned immediately. abort2() never
returns a non-zero value.
kern_exec.c:
- `len' is always assigned inside the if-statement right below it.
tty_info.c:
- `td' is always overwritten by FOREACH_THREAD_IN_PROC().
Found by: LLVM's scan-build
The last half year I've been working on a replacement TTY layer for the
FreeBSD kernel. The new TTY layer was designed to improve the following:
- Improved driver model:
The old TTY layer has a driver model that is not abstract enough to
make it friendly to use. A good example is the output path, where the
device drivers directly access the output buffers. This means that an
in-kernel PPP implementation must always convert network buffers into
TTY buffers.
If a PPP implementation would be built on top of the new TTY layer
(still needs a hooks layer, though), it would allow the PPP
implementation to directly hand the data to the TTY driver.
- Improved hotplugging:
With the old TTY layer, it isn't entirely safe to destroy TTY's from
the system. This implementation has a two-step destructing design,
where the driver first abandons the TTY. After all threads have left
the TTY, the TTY layer calls a routine in the driver, which can be
used to free resources (unit numbers, etc).
The pts(4) driver also implements this feature, which means
posix_openpt() will now return PTY's that are created on the fly.
- Improved performance:
One of the major improvements is the per-TTY mutex, which is expected
to improve scalability when compared to the old Giant locking.
Another change is the unbuffered copying to userspace, which is both
used on TTY device nodes and PTY masters.
Upgrading should be quite straightforward. Unlike previous versions,
existing kernel configuration files do not need to be changed, except
when they reference device drivers that are listed in UPDATING.
Obtained from: //depot/projects/mpsafetty/...
Approved by: philip (ex-mentor)
Discussed: on the lists, at BSDCan, at the DevSummit
Sponsored by: Snow B.V., the Netherlands
dcons(4) fixed by: kan
The ttyinfo() routine generates the fancy output when pressing ^T. Right
now it is stored in tty.c. In the MPSAFE TTY code it is already stored
in tty_info.c. To make integration of the MPSAFE TTY code a little
easier, take the same approach.
This makes the TTY code a little bit more readable, because having the
proc_*/thread_* routines in tty.c is very distractful.
Approved by: philip (mentor)
