Now that it is not used after schedlock changes got merged.
Note the unlock routine temporarily still checks for it on account of just using
regular spin unlock.
This is a prelude towards a general clean up.
Don't hold the scheduler lock while doing context switches. Instead we
unlock after selecting the new thread and switch within a spinlock
section leaving interrupts and preemption disabled to prevent local
concurrency. This means that mi_switch() is entered with the thread
locked but returns without. This dramatically simplifies scheduler
locking because we will not hold the schedlock while spinning on
blocked lock in switch.
This change has not been made to 4BSD but in principle it would be
more straightforward.
Discussed with: markj
Reviewed by: kib
Tested by: pho
Differential Revision: https://reviews.freebsd.org/D22778
Eliminate lock recursion from turnstiles. This was simply used to avoid
tracking the top-level turnstile lock. explicitly check for it before
picking up and dropping locks.
Reviewed by: kib
Tested by: pho
Differential Revision: https://reviews.freebsd.org/D22746
Do all sleepqueue post-processing in sleepq_remove_thread() so that we
do not require the thread lock after a context switch.
Reviewed by: jhb, kib
Differential Revision: https://reviews.freebsd.org/D22745
The arm kernel stack unwinder has apparently never been able to unwind when
the path of execution leads through a kernel module. There was code that
tried to handle modules by looking for the unwind data in them, but it did
so by trying to find symbols which have never existed in arm kernel
modules. That caused the unwind code to panic, and because part of panic
handling calls into the unwind code, that just created a recursion loop.
Locating the unwind data in a loaded module requires accessing the Elf
section headers to find the SHT_ARM_EXIDX section. For preloaded modules
those headers are present in a metadata blob. For dynamically loaded
modules, the headers are present only while the loading is in progress; the
memory is freed once the module is ready to use. For that reason, there is
new code in kern/link_elf.c, wrapped in #ifdef __arm__, to extract the
unwind info while the headers are loaded. The values are saved into new
fields in the linker_file structure which are also conditional on __arm__.
In arm/unwind.c there is new code to locally cache the per-module info
needed to find the unwind tables. The local cache is crafted for lockless
read access, because the unwind code often needs to run in context where
sleeping is not allowed. A large comment block describes the local cache
list, so I won't repeat it all here.
Eliminate recursion from most thread_lock consumers. Return from
sched_add() without the thread_lock held. This eliminates unnecessary
atomics and lock word loads as well as reducing the hold time for
scheduler locks. This will eventually allow for lockless remote adds.
Discussed with: kib
Reviewed by: jhb
Tested by: pho
Differential Revision: https://reviews.freebsd.org/D22626
an exclusive object lock.
Previously swap space was freed on a best effort basis when a page that
had valid swap was dirtied, thus invalidating the swap copy. This may be
done inconsistently and requires the object lock which is not always
convenient.
Instead, track when swap space is present. The first dirty is responsible
for deleting space or setting PGA_SWAP_FREE which will trigger background
scans to free the swap space.
Simplify the locking in vm_fault_dirty() now that we can reliably identify
the first dirty.
Discussed with: alc, kib, markj
Differential Revision: https://reviews.freebsd.org/D22654
exec_map_first_page(). This will also enable pagein clustering for other
interested consumers (tmpfs, md, etc).
Discussed with: alc
Approved by: kib
Differential Revision: https://reviews.freebsd.org/D22731
bits, by storing and modifying the complement of the original leaf
mask, and by avoiding some unnecessary intermediate variables in
computing the shift amounts. The logic is similar to what has recently
been committed to sys/sys/bitstring.h.
Compute better hint updates for the case when the cursor starts in
mid-leaf, and eliminates some otherwise viable solutions. Assume the
worst case, that all the eliminated offsets could have been solutions,
and you can still compute a better hint than we use now.
Eliminate some unnecessary conditional control flow.
Approved by: alc
Tested by: pho
Differential Revision: https://reviews.freebsd.org/D22666
Delay the attachment of children, when requested, until after interrutps are
running. This is often needed to allow children to run transactions on i2c or
spi busses. It's a common enough idiom that it will be useful to have its own
wrapper.
Reviewed by: ian
Differential Revision: https://reviews.freebsd.org/D21465
Allocate the callout structure on-demand from
fail_point_use_timeout_path() since most fail points do not use
timeouts.
Reviewed by: markj (earlier version), cem
Differential Revision: https://reviews.freebsd.org/D22599
s/BIT_NAND/BIT_ANDNOT/, and for CPU and DOMAINSET too. The actual
implementation is "and not" (or "but not"), i.e. A but not B.
Fortunately this does appear to be what all existing callers want.
Don't supply a NAND (not (A and B)) operation at this time.
Discussed with: jeff
Reviewed by: cem
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D22791
The simulation cannot be reproduced, so the value of using a deterministic PRNG
like random(3) is dubious. The number of repitions used in the sample isn't a
problem for the Chacha implementation of arc4random we have today. (Also, no
one actually runs this code; it was provided as an example of the work the
author did validating the implementation. It's not even test code.)
r355677 modified the NFS client so that it does lseek(SEEK_DATA/SEEK_HOLE)
for NFSv4.2, but calls vop_stdioctl() otherwise. As such, vop_stdioctl()
needs to be a global function.
Missed during the code merge for r355677.
via sys_sync(2). Minor cleanup, no functional changes.
Reviewed by: kib
MFC after: 2 weeks
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D19366
This fixes a regression after r355311. Specifically, sched_preempt()
may trigger a context switch by calling thread_lock(), since
thread_lock() calls critical_exit() in its slow path and the interrupted
thread may have already been marked for preemption. This would happen
before tdq_ipipending is cleared, blocking further preemption IPIs. The
CPU can be left in this state indefinitely if the interrupted thread
migrates.
Rename tdq_ipipending to tdq_owepreempt. Any switch satisfies a remote
preemption request, so clear tdq_owepreempt in sched_switch() instead of
sched_preempt() to avoid subtle problems of the sort described above.
Reviewed by: jeff, kib
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D22758
Both of these features are not needed by many consumers and result in avoidable
reads which in turn puts them on profiles due to cache-line ping ponging.
On top of that the current lockgmr entry point is slower than necessary
single-threaded. As an attempted clean up preparing for other changes,
provide new routines which don't support any of the aforementioned features.
With these patches in place vop_stdlock and vop_stdunlock disappear from
flamegraphs during -j 104 buildkernel.
Reviewed by: jeff (previous version)
Tested by: pho
Differential Revision: https://reviews.freebsd.org/D22665
A system call number should be at least reserved.
We do not expect an attempt to register a fixed number system call
when nothing at all is known about it.
MFC after: 3 weeks
Sponsored by: Panzura
This typedef is the same as timeout_t except that it is in the callout
namespace and header.
Use this typedef in various places of the callout implementation that
were either using the raw type or timeout_t.
While here, add <sys/callout.h> to the manpage.
Reviewed by: kib, imp
MFC after: 1 month
Differential Revision: https://reviews.freebsd.org/D22751
Partially revert r354741 and r354754 and go back to allocating a
fixed-size chunk of stack space for the auxiliary vector. Keep
sv_copyout_auxargs but change it to accept the address at the end of
the environment vector as an input stack address and no longer
allocate room on the stack. It is now called at the end of
copyout_strings after the argv and environment vectors have been
copied out.
This should fix a regression in r354754 that broke the stack alignment
for newer Linux amd64 binaries (and probably broke Linux arm64 as
well).
Reviewed by: kib
Tested on: amd64 (native, linux64 (only linux-base-c7), and i386)
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D22695
The current vnode layout is not smp-friendly by having frequently read data
avoidably sharing cachelines with very frequently modified fields. In
particular v_iflag inspected for VI_DOOMED can be found in the same line with
v_usecount. Instead make it available in the same cacheline as the v_op, v_data
and v_type which all get read all the time.
v_type is avoidably 4 bytes while the necessary data will easily fit in 1.
Shrinking it frees up 3 bytes, 2 of which get used here to introduce a new
flag field with a new value: VIRF_DOOMED.
Reviewed by: kib, jeff
Differential Revision: https://reviews.freebsd.org/D22715
1. replace hand-rolled macros for operation type with enum
2. unlock the vnode in vput itself, there is no need to branch on it. existence
of VPUTX_VPUT remains significant in that the inactive variant adds LK_NOWAIT
to locking request.
3. remove the useless v_usecount assertion. few lines above the checks if
v_usecount > 0 and leaves. should the value be negative, refcount would fail.
4. the CTR return vnode %p to the freelist is incorrect as vdrop may find the
vnode with holdcnt > 1. if the like should exist, it should be moved there
5. no need to error = 0 for everyone
Reviewed by: kib, jeff (previous version)
Differential Revision: https://reviews.freebsd.org/D22718
As mandated by POSIX. Also clarify the kill(2) manpage.
While there, restructure the code in killpg1() to use helper which
keeps overall state of the process list iteration in the killpg1_ctx
structued, later used to infer the error returned.
Reported by: amdmi3
Reviewed by: jilles
Sponsored by: The FreeBSD Foundation
MFC after: 2 weeks
Differential revision: https://reviews.freebsd.org/D22621
Use the power of variable to avoid spelling out source and generated
files too many times. The previous Makefiles were hard to read, hard to
edit, and badly formatted.
Reviewed by: kevans, emaste
Sponsored by: DARPA, AFRL
Differential Revision: https://reviews.freebsd.org/D22714
Two changes to EPOCH_TRACE:
(1) add a sysctl to surpress the backtrace from epoch_trace_report().
Sometimes the log line for the recursion is enough and the
backtrace massively spams the console.
(2) In order to be able to go without the backtrace do not only
print where the previous occurance happened, but also where
the current one happens. That way we have file:line information
for both and can look at them without the need for getting line
numbers from backtrace and a debugging tool.
Reviewed by: glebius
Sponsored by: Netflix (originally)
Differential Revision: https://reviews.freebsd.org/D22641
First, this removes a spurious difference compared to rw locks.
More importantly though this avoids a trip through sleepq code if the lock
happens to be caught in this state.
The mbuf zones were explicitly specifying the uma trash procedures on
zcreate, conditionally on INVARIANTS, because that used to be necessary
in order to get use-after-free checking for uma zones with non-empty
constructors or destructors. After r355137 uma automatically invokes
the trash constructor and destructor as long as no init and fini are
specified. This now allows the mbuf zones to pass their constructors
and destructors without needing to add on the uma trash procedures
conditionally.
Reviewed by: cem, jhb, markj
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D22583
- Use ustringp for the location of the argv and environment strings
and allow destp to travel further down the stack for the stackgap
and auxv regions.
- Update the Linux copyout_strings variants to move destp down the
stack as was done for the native ABIs in r263349.
- Stop allocating a space for a stack gap in the Linux ABIs. This
used to hold translated system call arguments, but hasn't been used
since r159992.
Reviewed by: kib
Tested on: md64 (amd64, i386, linux64), i386 (i386, linux)
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D22501
the vnode, logical block number, and size of data block that is
being requested. They then use the VOP_BMAP function to calculate
the mapping from logical block number to physical block number from
which to access the data. This change expands the interface to also
pass the physical block number in cases where the VOP_MAP function
may no longer work, for example when a file is being truncated.
No functional change.
Reviewed by: kib
Tested by: Peter Holm
Sponsored by: Netflix
Generally, it's preferred that an application fork/setsid if it doesn't want
to keep its controlling TTY, but it could be that a debugger is trying to
steal it instead -- so it would hook in, drop the controlling TTY, then do
some magic to set things up again. In this case, TIOCNOTTY is quite handy
and still respected by at least OpenBSD, NetBSD, and Linux as far as I can
tell.
I've dropped the note about obsoletion, as I intend to support TIOCNOTTY as
long as it doesn't impose a major burden.
Reviewed by: bcr (manpages), kib
Differential Revision: https://reviews.freebsd.org/D22572
