Suppose the following scenario:
1. Thread A holds a mutex.
2. Thread B goes to acquire the mutex, winds up in kernel waiting.
3. Thread A unlocks; first unsets the LOCKED flag.
As WAITING is set, it calls the kernel; but instead of processing
this immediately, the thread is suspended for any reason (locks,
reschedule, etc.)
4. Thread B hits a timeout, or a signal. It then unblocks in the kernel,
which causes the WAITING flag to be unset.
5. Thread C goes to acquire the lock. It sets the LOCKED flag.
It sees the WAITING flag is not set, so it returns at once,
having successfully acquired the lock.
6. Thread A, suspended back in step 3, resumes.
Now we encounter the problem. Under the previous code, the following
would occur.
7. Thread A sees that no threads are waiting. It thus unsets the LOCKED
flag, and returns from the kernel. Now we have a mutex theoretically
held by thread C but which (illegally) has no LOCKED flag set!
8. Some other thread tries to acquire the lock, and succeeds, for LOCKED
is not set. We now have one lock owned by two separate threads.
That's very bad!
The solution, in this commit, is to (1) switch from using "atomic_or"
to lock mutexes, to using "atomic_test_and_set", and (2) mandate that
_kern_unblock_mutex must be invoked with the mutex already unlocked.
Trying to solve the problem with (2) but without (1) produces other
complications and would overall be more complicated. For instance,
all existing userland code expected that it would set LOCKED, but then
check LOCKED|WAITING. If _kern_mutex_unlock does not unset LOCKED,
then whichever thread sets LOCKED when it was previously unset is
now the mutex's undisputed owner, and if it fails to notice this,
would deadlock.
That could have been solved with extra checks at all lock points, but
then that would mean locks would not be acquired "fairly": it would
be possible for any thread to race with an unlocking thread, and
acquire the lock before the kernel had a chance to wake anyone up.
Given how fast atomics can be, and how slow invoking the kernel is
comparatively, that would probably make our mutexes extremely "unfair."
This would not violate the POSIX specification, but it does seem like
a dangerous choice to make in implementing these APIs.
Linux's "futex" API, which our API bears some similarities to, requires
at least one atomic test-and-set for an uncontended acquisition,
and multiple atomics more for even the simplest case of contended
acquisition. If it works for them, it should work for us, too.
Fixes#18436.
Change-Id: Ib8c28acf04ce03234fe738e41aa0969ca1917540
Reviewed-on: https://review.haiku-os.org/c/haiku/+/6537
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>
Reviewed-by: Adrien Destugues <pulkomandy@pulkomandy.tk>
Reviewed-by: waddlesplash <waddlesplash@gmail.com>
- Stored the additional start time of each team, expressed by
milliseconds since boot.
- Added more fields to the `team_info` structure. These field
include those provided by the `get_extended_team_info` syscall as
well as the newly introduced `start_time`.
- Extended the `_kern_get_team_info` system call to receive an
additional `size_t` argument. If this size is smaller than or
equal to the size of the old `team_info` structure, the newly
added attributes will not be retrieved.
Change-Id: I22ee6b91ad2ee3b66a7f770036c79a718c5f115c
Reviewed-on: https://review.haiku-os.org/c/haiku/+/6390
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>
Reviewed-by: Jessica Hamilton <jessica.l.hamilton@gmail.com>
* This will be needed for the following commit that implements
`pthread_tryjoin_np` and `pthread_timedjoin_np`.
Change-Id: Idccb1aa588d6d10825294d14925d9bd046b65f19
Reviewed-on: https://review.haiku-os.org/c/haiku/+/5098
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>
Reviewed-by: Jérôme Duval <jerome.duval@gmail.com>
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>
the preallocate syscall will call the preallocate filesystem hook, if available.
fix#6285
Change-Id: Ifff4595548610c8e009d4e5ffb64c37e0884e62d
Reviewed-on: https://review.haiku-os.org/c/haiku/+/3382
Reviewed-by: Jérôme Duval <jerome.duval@gmail.com>
* Fixes problems with setting the partition name after uninitializing
a partition in DriveSetup. Previously, UninitializeJob() was
followed by SetStringJob(), but the kernel was updating the
change counter for the parent partition when uninitializing a
partition, leading to SetStringJob() having an incorrect change
counter for the parent partition. Now the parent change counter
will be correct when SetStringJob() runs.
Reduce duplication of code by
* Removing from elf_common.h definitions available in os/kernel/elf.h
* Deleting elf32.h and elf64.h
* Renaming elf_common.h to elf_private.h
* Updating source to build using public and private ELF header files
together
Signed-off-by: Jessica Hamilton <jessica.l.hamilton@gmail.com>
* Instead of letting the kernel search for the syslog port, the
daemon now registers itself with the kernel (which even solves
a TODO).
* A port is created for the actual log messages from the launch_daemon,
and used on start.
* However, the SyslogTest does not yet work, due to the BMessage <->
KMessage communication problems.
* Fixes sharing semantics, so non-shared semaphores in non-shared
memory do not become shared after a fork.
* Adds two new system calls: _user_mutex_sem_acquire/release(),
which reuse the user_mutex address-hashed wait mechanism.
* Named semaphores continue to use traditional sem_id semaphores.
The get_stack_trace syscall generates a stack trace using the kernel
debugging facilities and copies the resulting return address array to
the preallocated buffer from userland. It is only possible to get a
stack trace of the current thread.
The lookup_symbol syscall can be used to look up the symbol and image
name corresponding to an address. It can be used to resolve symbols
from a stack trace generated by the get_stack_trace syscall. Only
symbols of the current team can be looked up. Note that this uses
the symbol lookup of the kernel debugger which does not support lookup
of all symbols (static functions are missing for example).
This is meant to be used in situations where more elaborate stack trace
generation, like done in the userland debugging helpers, is not possible
due to constraints.
Reused x86 arch_user_debugger.cpp, with a few minor changes to make
the code work for both 32 and 64 bit. Something isn't quite working
right, if a breakpoint is hit the kernel will hang. Other than that
everything appears to work correctly.
The cookie is used to store the base address of the area that was just
visited. On 64-bit systems, int32 is not sufficient. Therefore, changed
to ssize_t which retains compatibility on x86 while expanding to a
sufficient size on x86_64.
Since this argument may be used to pass pointers, uint32 is not
correct for 64-bit. Effectively no change on 32-bit targets, both
size_t and uint32 are unsigned long there.
directory of a file without traversing leaf links (just like lstat()).
* Minor cleanup.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@42620 a95241bf-73f2-0310-859d-f6bbb57e9c96
address protection bits as well as the wiring flags for an arbitrary address
in a team's address space. Will be used in the debugger for the purposes
of the memory inspector/editor, in order to determine whether it can in fact
allow editing for the currently inspected address range.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@42129 a95241bf-73f2-0310-859d-f6bbb57e9c96
* Reorganized the kernel locking related to threads and teams.
* We now discriminate correctly between process and thread signals. Signal
handlers have been moved to teams. Fixes#5679.
* Implemented real-time signal support, including signal queuing, SA_SIGINFO
support, sigqueue(), sigwaitinfo(), sigtimedwait(), waitid(), and the addition
of the real-time signal range. Closes#1935 and #2695.
* Gave SIGBUS a separate signal number. Fixes#6704.
* Implemented <time.h> clock and timer support, and fixed/completed alarm() and
[set]itimer(). Closes#5682.
* Implemented support for thread cancellation. Closes#5686.
* Moved send_signal() from <signal.h> to <OS.h>. Fixes#7554.
* Lots over smaller more or less related changes.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@42116 a95241bf-73f2-0310-859d-f6bbb57e9c96
* inherit umask of calling process to images loaded via exec...()
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@40071 a95241bf-73f2-0310-859d-f6bbb57e9c96
only a few events can be watched (team creation/deletion/exec, thread creation/
deletion/name changes). The functions start_system_watching()/
stop_system_watching start/stop watching events.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@39862 a95241bf-73f2-0310-859d-f6bbb57e9c96
* _kern_[sg]et_timezone() now accepts/passes out the timezone name, too
* adjust Time preflet and clockconfig to pass the timezone name into the kernel
when calling _kern_set_timezone()
* ajust implementation of tzset() to fetch the timezone name from the kernel
via _kern_get_timezone() instead of reading 'libroot_timezone_info'
* the Time preflet no longer writes 'libroot_timezone_info'
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@38164 a95241bf-73f2-0310-859d-f6bbb57e9c96
* dropped DaylightSavingTime from real_time_clock code in kernel, it was
never really being used for what it meant (and just being referred to by
gettimeofday(), which put a different meaning to it
* adjusted the syscalls get_timezone() & set_timezone() as well as their callers
accordingly
* got rid of get_rtc_info() and rtc_info struct in kernel, as it was only
being referred to by the FAT add-on and that one (like gettimeofday()) put a
different meaning to tz_minuteswest. Added a comment to FAT's util.c
showing a possible solution, should the hardcoded GMT timezone pose a problem.
* fixed declaration of gettimeofday() to match POSIX base specs, issue 7
* changed implementation of gettimeofday() to not bother trying to fill struct
timezone - it was using wrong values before, anyway.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@37888 a95241bf-73f2-0310-859d-f6bbb57e9c96
* renamed syscalls _kern_[gs]et_tzfilename
to _kern_[gs]et_real_time_clock_is_gmt, as the filename part is no longer
relevant (and the two corresponding parameters were removed)
* C++-ified and reworked clockconfig to use the info from 'Time settings'
to setup the timezone info during boot
* removed invocation of _kern_get_tzfilename() from tzset(), as the syscall
no longer exists and tzset() is currently broken anyway
* adjusted the Time preflet to use the renamed syscall when getting/setting
the RTC info
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@37881 a95241bf-73f2-0310-859d-f6bbb57e9c96
of consistency.
* Moved the B_OVERCOMMITTING_AREA flag from B_KERNEL_AREA_FLAGS to
B_USER_AREA_FLAGS, since we really allow it to be passed from userland.
* Most VM syscalls check the provided protection against B_USER_AREA_FLAGS
instead of B_USER_PROTECTION, now. This way they allow for
B_OVERCOMMITTING_AREA as well.
* _user_map_file(), _user_set_memory_protection(): Check the protection like
the other syscalls do and use fix_protection() instead of doing that
manually.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@36572 a95241bf-73f2-0310-859d-f6bbb57e9c96
* Implemented a tiny bit more sophisticated version of
estimate_max_scheduling_latency() that uses a syscall that lets the scheduler
decide.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@36170 a95241bf-73f2-0310-859d-f6bbb57e9c96
locks.
* Added syscalls for a new kind of mutex. A mutex consists only of an int32 and
doesn't require any kernel resources. So it's initialization cannot fail
(it consists only of setting the mutex value to 0). An uncontended lock or
unlock operation can basically consist of an atomic_*() in userland. The
syscalls (when the mutex is contended) are a bit more expensive than semaphore
operations, though.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@36158 a95241bf-73f2-0310-859d-f6bbb57e9c96
* Implemented renameat(), faccessat(), fchownat(), fchmodat(), and mkfifoat().
* Added stub for mknodat().
* The kernel backend for faccessat() does not yet differentiate between
effective and real user/group IDs, though.
* Removed B_ENABLE_INCOMPLETE_POSIX_AT_SUPPORT, as we now support everything
(more or less). This also closes ticket #4928.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@34288 a95241bf-73f2-0310-859d-f6bbb57e9c96
each attribute access needed 3 syscalls, now only one as it should.
* Renamed the new Haiku call fs_open_attr() to fs_fopen_attr(), and added a new
function fs_open_attr() that takes a path (same semantics as the
fs_[f]open_attr_dir() functions already present in BeOS).
* Merged former _kern_open_attr(), and _kern_create_attr() into one syscall.
* Cleaned up vfs.h.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@31881 a95241bf-73f2-0310-859d-f6bbb57e9c96
functions.
* Since we now use UserStringParameter, this fixes the missing null termination
of the parameter string, and thus bug #4045.
* Removed UserMemoryParameter, as it's no longer in use.
* Adjusted syscalls accordingly.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@31779 a95241bf-73f2-0310-859d-f6bbb57e9c96
there are prefixed with the respective architecture name. Useful for remote
debugging a different architecture.
* <x86/arch_debugger.h>: Introduced a structure for the FPU state, so that it
isn't left to the debugger.
* Removed the _kern_get_thread_cpu_state() syscall. Was originally intended for
bdb compatiblity, but isn't really needed.
* Kernel x86 arch_get_debug_cpu_state(): The use of fnsave was broken, since
it reinits the FPU after saving the state. This resulted in weird results
when debugging functions using the FPU. We now use fxsave, if available.
Otherwise fnsave + frstor should be used -- not fully implemented yet.
Same for arch_set_debug_cpu_state().
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@31682 a95241bf-73f2-0310-859d-f6bbb57e9c96
and added a _kern_unreserve_address_range() as well.
* The runtime loader now reserves the space needed for all its areas first
to make sure there is enough space left for all areas of a single image.
* This also fixes the final part of bug #4008.
* Minor cleanup.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@31115 a95241bf-73f2-0310-859d-f6bbb57e9c96
the first part of making the runtime loader behave itself; it should already
make Clockwerk run okay with any number of translators (even if not all of
them will work yet).
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@31113 a95241bf-73f2-0310-859d-f6bbb57e9c96
