as this happens via thread_switchout(). I don't particularly like the
structure of the code here. We twice call out to thread code when
a thread is voluntarily switching. Once to thread_switchout() and once
to slot_fill(), while sched_4BSD does even more work which is redundant
to select another thread to use our remaining slice. This should be
simplified in the future, but for now I'm only going to fix the bug not
the bad design.
mutex instead of a MTX_DEF one in order to defer preemption while
reading the date and time registers. If we don't manage to read them
within the time slot where we are guaranteed that no updates occur we
might actually read them during an update in which case the output is
undefined.
aio_write(2) completion through kevent(2). This method does not work on
64-bit architectures. It was deprecated in FreeBSD 4.4. See revisions
1.87 and 1.70.2.7.
Change aio_physwakeup() to call psignal(9) directly rather than indirectly
through a timeout(9). Discussed with: bde
Correct a bug introduced in revision 1.65 that could result in premature
delivery of a signal if an lio_listio(2) consisted of a mixture of
direct/raw and queued I/O operations. Observed by: tegge
Eliminate a field from struct kaioinfo that is now unused.
Reviewed by: tegge
slot for us. Previously, we would take two slots on every preempt, and
setrunqueue() would fix it up for us in the non threaded case. The
threaded case was simply broken.
- Clean up flags, prototypes, comments.
file's access time should be updated when it gets executed. A while
ago the mechanism used to exec was changed to use a more mmap based
mechanism and this behavior was broken as a side-effect of that.
A new vnode flag is added that gets set when the file gets executed,
and the VOP_SETATTR() vnode operation gets called. The underlying
filesystem is expected to handle it based on its own semantics, some
filesystems don't support access time at all. Those that do should
handle it in a way that does not block, does not generate I/O if possible,
etc. In particular vn_start_write() has not been called. The UFS code
handles it the same way as it would normally handle the access time if
a file was read - the IN_ACCESS flag gets set in the inode but no other
action happens at this point. The actual time update will happen later
during a sync (which handles all the necessary locking).
Got me into this: cperciva
Discussed with: a lot with bde, a little with kan
Showed patches to: phk, jeffr, standards@, arch@
Minor discussion on: arch@
audit event identifier associated with each system call, which will
be stored by makesyscalls.sh in the sy_auevent field of struct sysent.
For now, default the audit identifier on all system calls to AUE_NULL,
but in the near future, other BSM event identifiers will be used. The
mapping of system calls to event identifiers is many:one due to
multiple system calls that map to the same end functionality across
compatibility wrappers, ABI wrappers, etc.
Submitted by: wsalamon
Obtained from: TrustedBSD Project
allocators: a set of power-of-two UMA zones for small allocations, and the
VM page allocator for large allocations. In order to maintain unified
statistics for specific malloc types, kernel malloc maintains a separate
per-type statistics pool, which can be monitored using vmstat -m. Prior
to this commit, each pool of per-type statistics was protected using a
per-type mutex associated with the malloc type.
This change modifies kernel malloc to maintain per-CPU statistics pools
for each malloc type, and protects writing those statistics using critical
sections. It also moves to unsynchronized reads of per-CPU statistics
when generating coalesced statistics. To do this, several changes are
implemented:
- In the previous world order, the statistics memory was allocated by
the owner of the malloc type structure, allocated statically using
MALLOC_DEFINE(). This embedded the definition of the malloc_type
structure into all kernel modules. Move to a model in which a pointer
within struct malloc_type points at a UMA-allocated
malloc_type_internal data structure owned and maintained by
kern_malloc.c, and not part of the exported ABI/API to the rest of
the kernel. For the purposes of easing a possible MFC, re-use an
existing pointer in 'struct malloc_type', and maintain the current
malloc_type structure size, as well as layout with respect to the
fields reused outside of the malloc subsystem (such as ks_shortdesc).
There are several unused fields as a result of no longer requiring
the mutex in malloc_type.
- Struct malloc_type_internal contains an array of malloc_type_stats,
of size MAXCPU. The structure defined above avoids hard-coding a
kernel compile-time value of MAXCPU into kernel modules that interact
with malloc.
- When accessing per-cpu statistics for a malloc type, surround read -
modify - update requests with critical_enter()/critical_exit() in
order to avoid races during write. The per-CPU fields are written
only from the CPU that owns them.
- Per-CPU stats now maintained "allocated" and "freed" counters for
number of allocations/frees and bytes allocated/freed, since there is
no longer a coherent global notion of the totals. When coalescing
malloc stats, accept a slight race between reading stats across CPUs,
and avoid showing the user a negative allocation count for the type
in the event of a race. The global high watermark is no longer
maintained for a malloc type, as there is no global notion of the
number of allocations.
- While tearing up the sysctl() path, also switch to using sbufs. The
current "export as text" sysctl format is retained with the same
syntax. We may want to change this in the future to export more
per-CPU information, such as how allocations and frees are balanced
across CPUs.
This change results in a substantial speedup of kernel malloc and free
paths on SMP, as critical sections (where usable) out-perform mutexes
due to avoiding atomic/bus-locked operations. There is also a minor
improvement on UP due to the slightly lower cost of critical sections
there. The cost of the change to this approach is the loss of a
continuous notion of total allocations that can be exploited to track
per-type high watermarks, as well as increased complexity when
monitoring statistics.
Due to carefully avoiding changing the ABI, as well as hardening the ABI
against future changes, it is not necessary to recompile kernel modules
for this change. However, MFC'ing this change to RELENG_5 will require
also MFC'ing optimizations for soft critical sections, which may modify
exposed kernel ABIs. The internal malloc API is changed, and
modifications to vmstat in order to restore "vmstat -m" on core dumps will
follow shortly.
Several improvements from: bde
Statistics approach discussed with: ups
Tested by: scottl, others
Only panic is fixed, module will be still listed in kldstat(8) output.
Not sure what is correct fix, because adding unloading code in case of
failure to linker_init_kernel_modules() doesn't work.
of having the kernel parse that line and add an entry to the argument list for
each 'separate word' it finds, have it add only one entry which holds all
the words found on that line. The old behavior is useful in some situations,
but it does not match the way any other operating system will parse that line.
This has been discussed in the thread "Bug in #! processing - One More Time"
on the freebsd-arch mailing list (starting back on Feb 24, 2005). The first
few messages in that thread provide the background in much detail.
PR: 16393
Reviewed by: freebsd-arch
sysctl path. While this code is close to MPSAFE, it may require some
additional locking. Mark ntp_gettime1() as GIANT_REQUIRED for now.
Suggested by: phk
on the their simply wrapping MPSAFE implementations of existing MPSAFE
system calls:
getfsstat()
lseek()
stat()
lstat()
truncate()
ftruncate()
statfs()
fstatfs()
Note that ogetdirentries() is not marked MPSAFE because it does not share
the MPSAFE implementation used for getdirentries(), and requires separate
locking to be implemented.
that protects socket and receive socket buffer state, and a second
mutex to protect send socket buffer state. In some places, the
mutex shared between the socket and receive socket buffer will be
acquired twice, once by each layer, resulting in some
inconsistency, but providing the abstraction benefit of being able
to more easily separate the two mutexes in the future if desired.
When transitioning a socket to the SS_ISDISCONNECTING or
SS_ISDISCONNECTED states, grab the socket/receive socket buffer lock
once rather than grabbing it as the socket lock, modifying socket
state, then grabbing a second time as the receive lock in order to
modify the socket buffer state to indicate no further data can be
read. This change is believed to close a race between the change in
socket state and the change in socket buffer state, which for a
remotely initiated close on a UNIX domain socket, resulted in
soreceive() returning ENOTCONN rather than an EOF condition.
A similar race still exists in the case of send, however, and is
harder to fix as the socket and send socket buffer mutexes are not
the same, and we would like to avoid holding combinations of socket
mutexes over sb_upcall until we've finished clarifying the locking
protocol for upcalls.
This change has the side affect of reducing the number of mutex
operations to initiate disconnect or perform disconnect on a
socket by two.
PR: 78824
Rerported by: Marc Olzheim <marcolz@stack.nl>
MFC after: 2 weeks
