application destroys semaphore after sem_wait returns. Just enter
kernel to wake up sleeping threads, only update _has_waiters if
it is safe. While here, check if the value exceed SEM_VALUE_MAX and
return EOVERFLOW if this is true.
a mutex after a thread has unlocked it, it event writes data to the mutex
memory to clear contention bit, there is a race that other threads
can lock it and unlock it, then destroy it, so it should not write
data to the mutex memory if there isn't any waiter.
The new operation UMTX_OP_MUTEX_WAKE2 try to fix the problem. It
requires thread library to clear the lock word entirely, then
call the WAKE2 operation to check if there is any waiter in kernel,
and try to wake up a thread, if necessary, the contention bit is set again
by the operation. This also mitgates the chance that other threads find
the contention bit and try to enter kernel to compete with each other
to wake up sleeping thread, this is unnecessary. With this change, the
mutex owner is no longer holding the mutex until it reaches a point
where kernel umtx queue is locked, it releases the mutex as soon as
possible.
Performance is improved when the mutex is contensted heavily. On Intel
i3-2310M, the runtime of a benchmark program is reduced from 26.87 seconds
to 2.39 seconds, it even is better than UMTX_OP_MUTEX_WAKE which is
deprecated now. http://people.freebsd.org/~davidxu/bench/mutex_perf.c
via procstat(1) and fstat(1):
- Change shm file descriptors to track the pathname they are associated
with and add a shm_path() method to copy the path out to a caller-supplied
buffer.
- Use the fo_stat() method of shared memory objects and shm_path() to
export the path, mode, and size of a shared memory object via
struct kinfo_file.
- Add a struct shmstat to the libprocstat(3) interface along with a
procstat_get_shm_info() to export the mode and size of a shared memory
object.
- Change procstat to always print out the path for a given object if it
is valid.
- Teach fstat about shared memory objects and to display their path,
mode, and size.
MFC after: 2 weeks
Kernel pointer values are used as opaque unique identifiers, which are then
used to reconstruct references between various providers, classes, etc., inside
libgeom from the source XML. Unfortunately, they're converted to pointer-width
integers (in the form of pointers) to do this, and 32-bit userland pointers
cannot hold sensible representations (however opaque) of 64-bit kernel pointers
on all systems.
In the case where the leading bits are zero and 32 distinct bits of pointer can
be identified, this will happen to work. On systems where the upper 32-bits of
kernel pointers are non-zero and the same for all kernel pointers, this will
result in double frees and all kinds of bizarre crashes and linkage between
objects inside libgeom.
To mitigate this problem, treat the opaque identifiers in the XML as C strings
instead, and internalize them to give unique and consistent per-object pointer
values in userland for each identifier in the XML. This allows us to keep the
libgeom logic the same with only minor changes to initial setup and parsing.
It might be more sensible for speed reasons to treat the identifiers as numbers
of a large size (uintmax_t, say) rather than strings, but strings seem fine for
now.
(As an added side-effect, this makes it slightly easier to identify unresolved
references, but nothing has been added to inform the user of those.)
New kernel events can be added at various location for sampling or counting.
This will for example allow easy system profiling whatever the processor is
with known tools like pmcstat(8).
Simultaneous usage of software PMC and hardware PMC is possible, for example
looking at the lock acquire failure, page fault while sampling on
instructions.
Sponsored by: NETASQ
MFC after: 1 month
pam_exec(8) now accepts a new option "return_prog_exit_status". When
set, the program exit status is used as the pam_exec return code. It
allows the program to tell why the step failed (eg. user unknown).
However, if it exits with a code not allowed by the calling PAM service
module function (see $PAM_SM_FUNC below), a warning is logged and
PAM_SERVICE_ERR is returned.
The following changes are related to this new feature but they apply no
matter if the "return_prog_exit_status" option is set or not.
The environment passed to the program is extended:
o $PAM_SM_FUNC contains the name of the PAM service module function
(eg. pam_sm_authenticate).
o All valid PAM return codes' numerical values are available
through variables named after the return code name. For instance,
$PAM_SUCCESS, $PAM_USER_UNKNOWN or $PAM_PERM_DENIED.
pam_exec return code better reflects what went on:
o If the program exits with !0, the return code is now
PAM_PERM_DENIED, not PAM_SYSTEM_ERR.
o If the program fails because of a signal (WIFSIGNALED) or doesn't
terminate normally (!WIFEXITED), the return code is now
PAM_SERVICE_ERR, not PAM_SYSTEM_ERR.
o If a syscall in pam_exec fails, the return code remains
PAM_SYSTEM_ERR.
waitpid(2) is called in a loop. If it returns because of EINTR, do it
again. Before, it would return PAM_SYSTEM_ERR without waiting for the
child to exit.
Several log messages now include the PAM service module function name.
The man page is updated accordingly.
Reviewed by: gleb@, des@
Sponsored by: Yakaz (http://www.yakaz.com)
MFC after: 2 weeks
- Rename pmc.mips to pmc.mips24k since it covers just one CPU,
no whole architecture
- Add documetnations for Octeon's PMC counters
- Remove CAVEATS section from pmc.mips24k page: PMC for MIPS supports
sampling now.
Because the utmpx interface is generally not required to be thread-safe,
but it is nice to have, if easy to do so. Therefore don't make a mess
out of the code and only use it if __NO_TLS is not defined.
