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* Use a generic way to back threads out of wait queues when handlingdeischen2004-12-181-3/+1
| | | | | | | | | | | | | | | | | | | | | | | | | signals instead of having more intricate knowledge of thread state within signal handling. Simplify signal code because of above (by David Xu). Use macros for libpthread usage of pthread_cleanup_push() and pthread_cleanup_pop(). This removes some instances of malloc() and free() from the semaphore and pthread_once() implementations. When single threaded and forking(), make sure that the current thread's signal mask is inherited by the forked thread. Use private mutexes for libc and libpthread. Signals are deferred while threads hold private mutexes. This fix also breaks www/linuxpluginwrapper; a patch that fixes it is at http://people.freebsd.org/~deischen/kse/linuxpluginwrapper.diff Fix race condition in condition variables where handling a signal (pthread_kill() or kill()) may not see a wakeup (pthread_cond_signal() or pthread_cond_broadcast()). In collaboration with: davidxu
* 1. Move thread list flags into new separate member, and atomicallydavidxu2004-10-231-0/+1
| | | | | | | | | | | put DEAD thread on GC list, this closes a race between pthread_join and thr_cleanup. 2. Introduce a mutex to protect tcb initialization, tls allocation and deallocation code in rtld seems no lock protection or it is broken, under stress testing, memory is corrupted. Reviewed by: deischen patch partly provided by: deischen
* As long as we have a knob to force system scope threads, why not havedeischen2004-08-121-1/+4
| | | | | | | | | | | | | a knob to force process scope threads. If the environment variable LIBPTHREAD_PROCESS_SCOPE is set, force all threads to be process scope threads regardless of how the application creates them. If LIBPTHREAD_SYSTEM_SCOPE is set (forcing system scope threads), it overrides LIBPTHREAD_PROCESS_SCOPE. $ # To force system scope threads $ LIBPTHREAD_SYSTEM_SCOPE=anything threaded_app $ # To force process scope threads $ LIBPTHREAD_PROCESS_SCOPE=anything threaded_app
* Add a way to force 1:1 mode for libpthread. To do this, definedeischen2004-08-071-3/+2
| | | | | | | | | | | LIBPTHREAD_SYSTEM_SCOPE in the environment. You can still force libpthread to be built in strictly 1:1 by adding -DSYSTEM_SCOPE_ONLY to CFLAGS. This is kept for archs that don't yet support M:N mode. Requested by: rwatson Reviewed by: davidxu
* Remove unused symbols.davidxu2004-07-131-14/+0
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* Check pending signals, if there is signal will be unblocked bydavidxu2004-06-121-0/+1
| | | | | | | | | | | | | | | | | | sigsuspend, thread shouldn't wait, in old code, it may be ignored. When a signal handler is invoked in sigsuspend, thread gets two different signal masks, one is in thread structure, sigprocmask() can retrieve it, another is in ucontext which is a third parameter of signal handler, the former is the result of sigsuspend mask ORed with sigaction's sa_mask and current signal, the later is the mask in thread structure before sigsuspend is called. After signal handler is called, the mask in ucontext should be copied into thread structure, and becomes CURRENT signal mask, then sigsuspend returns to user code. Reviewed by: deischen Tested by: Sean McNeil <sean@mcneil.com>
* Add a simple work-around for deadlocking on recursive read locksdeischen2004-01-081-0/+1
| | | | | | | | | | on a rwlock while there are writers waiting. We normally favor writers but when a reader already has at least one other read lock, we favor the reader. We don't track all the rwlocks owned by a thread, nor all the threads that own a rwlock -- we just keep a count of all the read locks owned by a thread. PR: 24641
* Implement sigaltstack() as per-threaded. Current only scope process threaddavidxu2003-12-291-0/+3
| | | | | | | | is supported, for scope system process, kernel signal bits need to be changed. Reviewed by: deischen Tested on : i386 amd64 ia64
* 1. Allocating and freeing lock related resource in _thr_alloc and _thr_freedavidxu2003-09-141-18/+20
| | | | | | | | | | | to avoid potential memory leak, also fix a bug in pthread_create, contention scope should be inherited when PTHREAD_INHERIT_SCHED is set, and also check right field for PTHREAD_INHERIT_SCHED, scheduling inherit flag is in sched_inherit. 2. Execute hooks registered by atexit() on thread stack but not on scheduler stack. 3. Simplify some code in _kse_single_thread by calling xxx_destroy functions. Reviewed by: deischen
* Fix an off by one error in the number of arguments passed tomarcel2003-08-061-1/+1
| | | | | | makecontext(). We only supply 3, not 4. This is mostly harmless, except that on ia64 the garbage can include NaT bits, resulting in NaT consumption faults.
* Rethink the MD interfaces for libpthread to account fordeischen2003-08-051-16/+14
| | | | | | | | | archs that can (or are required to) have per-thread registers. Tested on i386, amd64; marcel is testing on ia64 and will have some follow-up commits. Reviewed by: davidxu
* o Eliminate upcall for PTHREAD_SYSTEM_SCOPE thread, now itdavidxu2003-07-171-17/+25
| | | | | | | | | | | | | is system bound thread and when it is blocked, no upcall is generated. o Add ability to libkse to allow it run in pure 1:1 threading mode, defining SYSTEM_SCOPE_ONLY in Makefile can turn on this option. o Eliminate code for installing dummy signal handler for sigwait call. o Add hash table to find thread. Reviewed by: deischen
* Write new thread pointer back only when success.davidxu2003-06-281-3/+4
| | | | Reviewed by: deischen
* KMF_DONE is now in /sys/sys/kse.h, no longer need to define it here.davidxu2003-06-041-3/+0
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* Change low-level locking a bit so that we can tell ifdeischen2003-05-241-24/+9
| | | | | | | | | | | | | | | | | | | | | | | | | | a lock is being waitied on. Fix a races in join and cancellation. When trying to wait on a CV and the library is not yet threaded, make it threaded so that waiting actually works. When trying to nanosleep() and we're not threaded, just call the system call nanosleep instead of adding the thread to the wait queue. Clean up adding/removing new threads to the "all threads queue", assigning them unique ids, and tracking how many active threads there are. Do it all when the thread is added to the scheduling queue instead of making pthread_create() know how to do it. Fix a race where a thread could be marked for signal delivery but it could be exited before we actually add the signal to it. Other minor cleanups and bug fixes. Submitted by: davidxu Approved by: re@ (blanket for libpthread)
* Fix suspend and resume.deischen2003-05-041-1/+3
| | | | Submitted (in part) by: Kazuaki Oda <kaakun@highway.ne.jp>
* Move the mailbox to the beginning of the thread and align thedeischen2003-04-301-0/+3
| | | | thread so that the context (SSE FPU state) is also aligned.
* o Don't add a scope system thread's KSE to the list of availabledeischen2003-04-281-0/+7
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | KSEs when it's thread exits; allow the GC handler to do that. o Make spinlock/spinlock critical regions. The following were submitted by davidxu o Alow thr_switch() to take a null mailbox argument. o Better protect cancellation checks. o Don't set KSE specific data when creating new KSEs; rely on the first upcall of the KSE to set it. o Add the ability to set the maximum concurrency level and do this automatically. We should have a way to enable/disable this with some sort of tunable because some applications may not want this to be the default. o Hold the scheduling lock across thread switch calls. o If scheduling of a thread fails, make sure to remove it from the list of active threads. o Better protect accesses to a joining threads when the target thread is exited and detached. o Remove some macro definitions that are now provided by <sys/kse.h>. o Don't leave the library in threaded mode if creation of the initial KSE fails. o Wakeup idle KSEs when there are threads ready to run. o Maintain the number of threads active in the priority queue.
* Add a couple asserts to pthread_cond_foo to ensure the (low-level)deischen2003-04-221-1/+15
| | | | | | | | | | | | | | | lock level is 0. Thus far, the threads implementation doesn't use mutexes or condition variables so the lock level should be 0. Save the return value when trying to schedule a new thread and use this to return an error from pthread_create(). Change the max sleep time for an idle KSE to 1 minute from 2 minutes. Maintain a count of the number of KSEs within a KSEG. With these changes scope system threads seem to work, but heavy use of them crash the kernel (supposedly VM bugs).
* Add an i386-specifc hack to always set %gs. There still seemsdeischen2003-04-211-15/+39
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | to be instances where the kernel doesn't properly save and/or restore it. Use noupcall and nocompleted flags in the KSE mailbox. These require kernel changes to work which will be committed sometime later. Things still work without the changes. Remove the general kse entry function and use two different functions -- one for scope system threads and one for scope process threads. The scope system function is not yet enabled and we use the same function for all threads at the moment. Keep a copy of the KSE stack for the case that a KSE runs a scope system thread and uses the same stack as the thread (no upcalls are generated, so a separate stack isn't needed). This isn't enabled yet. Use a separate field for the KSE waiting flag. It isn't correct to use the mailbox flags field. The following fixes were provided by David Xu: o Initialize condition variable locks with thread versions of the low-level locking functions instead of the kse versions. o Enable threading before creating the first thread instead of after. o Don't enter critical regions when trying to malloc/free or call functions that malloc/free. o Take the scheduling lock when inheriting thread attributes. o Check the attribute's stack pointer instead of the attributes stack size for null when allocating a thread's stack. o Add a kseg reinit function so we don't have to destroy and then recreate the same lock. o Check the return value of kse_create() and return an appropriate error if it fails. o Don't forget to destroy a thread's locks when freeing it. o Examine the correct flags word for checking to see if a thread is in a synchronization queue. Things should now work on an SMP kernel.
* Sorry folks; I accidentally committed a patch from what I was workingdeischen2003-04-181-6/+7
| | | | | | on a couple of days ago. This should be the most recent changes. Noticed by: davidxu
* Revamp libpthread so that it has a chance of working in an SMPdeischen2003-04-181-94/+164
| | | | | | | | | | | | | | | | | | | environment. This includes support for multiple KSEs and KSEGs. The ability to create more than 1 KSE via pthread_setconcurrency() is in the works as well as support for PTHREAD_SCOPE_SYSTEM threads. Those should come shortly. There are still some known issues which davidxu and I are working on, but it'll make it easier for us by committing what we have. This library now passes all of the ACE tests that libc_r passes with the exception of one. It also seems to work OK with KDE including konqueror, kwrite, etc. I haven't been able to get mozilla to run due to lack of java plugin, so I'd be interested to see how it works with that. Reviewed by: davidxu
* Use KSE to schedule threads.mini2002-10-301-8/+8
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* Make libpthread KSE aware.mini2002-09-161-35/+8
| | | | | Reviewed by: deischen, julian Approved by: -arch
* Make the changes needed for libpthread to compile in its new home.mini2002-09-161-1/+1
| | | | | | | | The new libpthread will provide POSIX threading support using KSE. These files were previously repo-copied from src/lib/libc_r. Reviewed by: deischen Approved by: -arch
* Oops, forgot to set the suspended flag for threads that are createddeischen2002-07-091-2/+3
| | | | | | | initially suspended. This was preventing such threads from getting resumed. Reported by: Bill Huey <billh@gnuppy.monkey.org>
* Add the ability to recognize old references to keys, and return NULLdeischen2002-03-191-1/+1
| | | | | when old keys are referenced (after pthread_key_delete()) via pthread_getspecific().
* This has been sitting in my local tree long enough. Remove the usedeischen2002-02-091-8/+0
| | | | | | | | | | | | | | of an alternate signal stack for handling signals. Let the kernel send signals on the stack of the current thread and teach the threads signal handler how to deliver signals to the current thread if it needs to. Also, always store a threads context as a jmp_buf. Eventually this will change to be a ucontext_t or mcontext_t. Other small nits. Use struct pthread * instead of pthread_t in internal library routines. The threads code wants struct pthread *, and pthread_t doesn't necessarily have to be the same. Reviewed by: jasone
* Implement pthread_attr_[gs]etguardsize(). Non-default-size stacks used tojasone2001-07-201-62/+7
| | | | | | | | be malloc()ed, but they are now allocated using mmap(), just as the default-size stacks are. A separate cache of stacks is kept for non-default-size stacks. Collaboration with: deischen
* Instead of using a join queue for each thread, use a single pointer tojasone2001-05-201-2/+2
| | | | | | | | | | | keep track of a joiner. POSIX only supports a single joiner, so this simplification is acceptable. At the same time, make sure to mark a joined thread as detached so that its resources can be freed. Reviewed by: deischen PR: 24345
* To be consistent, use the __weak_reference macro from <sys/cdefs.h>deischen2001-04-101-1/+1
| | | | | | instead of #pragma weak to create weak definitions. Suggested by: bde
* Add weak definitions for wrapped system calls. In general:deischen2001-01-241-8/+11
| | | | | | | | | | | | | | | | | | | | | | | | | | | _foo - wrapped system call foo - weak definition to _foo and for cancellation points: _foo - wrapped system call __foo - enter cancellation point, call _foo(), leave cancellation point foo - weak definition to __foo Change use of global _thread_run to call a function to get the currently running thread. Make all pthread_foo functions weak definitions to _pthread_foo, where _pthread_foo is the implementation. This allows an application to provide its own pthread functions. Provide slightly different versions of pthread_mutex_lock and pthread_mutex_init so that we can tell the difference between a libc mutex and an application mutex. Threads holding mutexes internal to libc should never be allowed to exit, call signal handlers, or cancel. Approved by: -arch
* Don't needlessly poll file descriptors when there are nodeischen2000-11-091-21/+24
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | file descriptors needing to be polled (Doh!). Reported by Dan Nelson <dnelson@emsphone.com>. Don't install and start the scheduling timer until the first thread is created. This prevents the overhead of having a periodic scheduling signal in a single threaded program. Reported by Dan Nelson <dnelson@emsphone.com>. Allow builtin longjmps out of application installed signal handlers without the need perform any post-handler cleanup: o Change signal handling to save the threads interrupted context on the stack. The threads current context is now always stored in the same place (in the pthread). If and when a signal handler returns, the interrupted context is copied back to the storage area in the pthread. o Before calling invoking a signal handler for a thread, back the thread out of any internal waiting queues (mutex, CV, join, etc) to which it belongs. Rework uthread_info.c a bit to make it easier to change the format of a thread dump. Use an alternal signal stack for the thread library's signal handler. This allows us to fiddle with the main threads stack without fear of it being in use. Reviewed by: jasone
* Implement zero system call thread switching. Performance ofdeischen2000-10-131-61/+38
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | thread switches should be on par with that under scheduler activations. o Timing is achieved through the use of a fixed interval timer (ITIMER_PROF) to count scheduling ticks instead of retrieving the time-of-day upon every thread switch and calculating elapsed real time. o Polling for I/O readiness is performed once for each scheduling tick instead of every thread switch. o The non-signal saving/restoring versions of setjmp/longjmp are used to save and restore thread contexts. This may allow the removal of _THREAD_SAFE macros from setjmp() and longjmp() - needs more investigation. Change signal handling so that signals are handled in the context of the thread that is receiving the signal. When signals are dispatched to a thread, a special signal handling frame is created on top of the target threads stack. The frame contains the threads saved state information and a new context in which the thread can run. The applications signal handler is invoked through a wrapper routine that knows how to restore the threads saved state and unwind to previous frames. Fix interruption of threads due to signals. Some states were being improperly interrupted while other states were not being interrupted. This should fix several PRs. Signal handlers, which are invoked as a result of a process signal (not by pthread_kill()), are now called with the code (or siginfo_t if SA_SIGINFO was set in sa_flags) and sigcontext_t as received from the process signal handler. Modify the search for a thread to which a signal is delivered. The search algorithm is now: o First thread found in sigwait() with signal in wait mask. o First thread found sigsuspend()'d on the signal. o Current thread if signal is unmasked. o First thread found with signal unmasked. Collapse machine dependent support into macros defined in pthread_private.h. These should probably eventually be moved into separate MD files. Change the range of settable priorities to be compliant with POSIX (0-31). The threads library uses higher priorities internally for real-time threads (not yet implemented) and threads executing signal handlers. Real-time threads and threads running signal handlers add 64 and 32, respectively, to a threads base priority. Some other small changes and cleanups. PR: 17757 18559 21943 Reviewed by: jasone
* Fix pthread_suspend_np/pthread_resume_np. For the record, suspending adeischen2000-03-151-3/+2
| | | | | | | | | | | | | | thread waiting on an event (I/O, condvar, etc) will, when resumed using pthread_resume_np, return with EINTR. For example, suspending and resuming a thread blocked on read() will not requeue the thread for the read, but will return -1 with errno = EINTR. If the suspended thread is in a critical region, the thread is suspended as soon as it leaves the critical region. Fix a bogon in pthread_kill() where a signal was being delivered twice to threads waiting in sigwait(). Reported by (suspend/resume bug): jdp Reviewed by: jasone
* Implement continuations to correctly handle [sig|_]longjmp() inside of ajasone2000-01-191-11/+25
| | | | | | | | | | | | | | | | | | | | | | signal handler. Explicitly check for jumps to anywhere other than the current stack, since such jumps are undefined according to POSIX. While we're at it, convert thread cancellation to use continuations, since it's cleaner than the original cancellation code. Avoid delivering a signal to a thread twice. This was a pre-existing bug, but was likely unexposed until these other changes were made. Defer signals generated by pthread_kill() so that they can be delivered on the appropriate stack. deischen claims that this is unnecessary, which is likely true, but without this change, pthread_kill() can cause undefined priority queue states and/or PANICs in [sig|_]longjmp(), so I'm leaving this in for now. To compile this code out and exercise the bug, define the _NO_UNDISPATCH cpp macro. Defining _PTHREADS_INVARIANTS as well will cause earlier crashes. PR: kern/14685 Collaboration with: deischen
* Don't explicitly mmap() red zones at the bottom of thread stacks (exceptjasone1999-12-291-10/+1
| | | | | | | | | | the initial thread). Instead, just leave an unmapped gap between thread stacks and make sure that the thread stacks won't grow into these gaps, simply by limiting the size of the stacks with the 'len' argument to mmap(). This (if I understand correctly) reduces VM overhead considerably. Reviewed by: deischen
* Change stack allocation algorithm to make better use of memorydeischen1999-12-281-15/+15
| | | | | (it was leaving an unused block). Also protect the global stack pointer from context changes while fiddling with it.
* * Fix the stack allocation code so that it works for alpha. Change itdfr1999-11-281-5/+23
| | | | | | | | | to use mmap(..., MAP_STACK, ...) on alpha too since that should work now. * Add hooks to allow GDB to access the internals of pthreads without having to know the exact layout of struct pthread. Reviewed by: deischen
* add pthread_cancel, obtained from OpenBSD.alfred1999-11-281-2/+3
| | | | | | | | | | | | | | eischen (Daniel Eischen) added wrappers to protect against cancled threads orphaning internal resources. the cancelability code is still a bit fuzzy but works for test programs of my own, OpenBSD's and some examples from ORA's books. add readdir_r to both libc and libc_r add some 'const' attributes to function parameters Reviewed by: eischen, jasone
* $Id$ -> $FreeBSD$peter1999-08-281-1/+1
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* Add RCS IDs to those files without them.deischen1999-08-051-2/+2
| | | | | | | Fix copyrights (s/REGENTS/AUTHOR). Suggested by: tg Approved by: jb
* Fix a couple more coding style nits.jasone1999-07-111-2/+2
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* Modify previous changes to conform better to libc_r's coding style.jasone1999-07-111-35/+56
| | | | | | | | Always use mmap() for default-size stack allocation. Use MAP_ANON instead of MAP_STACK on the alpha architecture. Reduce the amount of code executed while owning _gc_mutex during stack allocation.
* Always use growable thread stacks on the i386. The VM_STACK kernel optionjasone1999-07-061-4/+2
| | | | | must be made default for the alpha before growable thread stacks are enabled for the alpha.
* Use growable stacks for thread stacks that are the default stack size.jasone1999-07-051-1/+57
| | | | | | | | | | | | | Cache discarded default thread stacks for use in subsequent thread creations. Create a red zone at the end of each stack (including the initial thread stack), with the hope of causing a segfault if a stack overflows. To activate these modifications, add -D_PTHREAD_GSTACK to CFLAGS in src/lib/libc_r/Makefile. Since the modifications depend on the VM_STACK kernel option, I'm not sure how to safely use growable stacks by default. Testing, as well as algorithmic and stylistic comments are welcome.
* In the words of the author:jb1999-06-201-22/+16
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | o The polling mechanism for I/O readiness was changed from select() to poll(). In additon, a wrapped version of poll() is now provided. o The wrapped select routine now converts each fd_set to a poll array so that the thread scheduler doesn't have to perform a bitwise search for selected fds each time file descriptors are polled for I/O readiness. o The thread scheduler was modified to use a new queue (_workq) for threads that need work. Threads waiting for I/O readiness and spinblocks are added to the work queue in addition to the waiting queue. This reduces the time spent forming/searching the array of file descriptors being polled. o The waiting queue (_waitingq) is now maintained in order of thread wakeup time. This allows the thread scheduler to find the nearest wakeup time by looking at the first thread in the queue instead of searching the entire queue. o Removed file descriptor locking for select/poll routines. An application should not rely on the threads library for providing this locking; if necessary, the application should use mutexes to protect selecting/polling of file descriptors. o Retrieve and use the kernel clock rate/resolution at startup instead of hardcoding the clock resolution to 10 msec (tested with kernel running at 1000 HZ). o All queues have been changed to use queue.h macros. These include the queues of all threads, dead threads, and threads waiting for file descriptor locks. o Added reinitialization of the GC mutex and condition variable after a fork. Also prevented reallocation of the ready queue after a fork. o Prevented the wrapped close routine from closing the thread kernel pipes. o Initialized file descriptor table for stdio entries at thread init. o Provided additional flags to indicate to what queues threads belong. o Moved TAILQ initialization for statically allocated mutex and condition variables to after the spinlock. o Added dispatching of signals to pthread_kill. Removing the dispatching of signals from thread activation broke sigsuspend when pthread_kill was used to send a signal to a thread. o Temporarily set the state of a thread to PS_SUSPENDED when it is first created and placed in the list of threads so that it will not be accidentally scheduled before becoming a member of one of the scheduling queues. o Change the signal handler to queue signals to the thread kernel pipe if the scheduling queues are protected. When scheduling queues are unprotected, signals are then dequeued and handled. o Ensured that all installed signal handlers block the scheduling signal and that the scheduling signal handler blocks all other signals. This ensures that the signal handler is only interruptible for and by non-scheduling signals. An atomic lock is used to decide which instance of the signal handler will handle pending signals. o Removed _lock_thread_list and _unlock_thread_list as they are no longer used to protect the thread list. o Added missing RCS IDs to modified files. o Added checks for appropriate queue membership and activity when adding, removing, and searching the scheduling queues. These checks add very little overhead and are enabled when compiled with _PTHREADS_INVARIANTS defined. Suggested and implemented by Tor Egge with some modification by me. o Close a race condition in uthread_close. (Tor Egge) o Protect the scheduling queues while modifying them in pthread_cond_signal and _thread_fd_unlock. (Tor Egge) o Ensure that when a thread gets a mutex, the mutex is on that threads list of owned mutexes. (Tor Egge) o Set the kernel-in-scheduler flag in _thread_kern_sched_state and _thread_kern_sched_state_unlock to prevent a scheduling signal from calling the scheduler again. (Tor Egge) o Don't use TAILQ_FOREACH macro while searching the waiting queue for threads in a sigwait state, because a change of state destroys the TAILQ link. It is actually safe to do so, though, because once a sigwaiting thread is found, the loop ends and the function returns. (Tor Egge) o When dispatching signals to threads, make the thread inherit the signal deferral flag of the currently running thread. (Tor Egge) Submitted by: Daniel Eischen <eischen@vigrid.com> and Tor Egge <Tor.Egge@fast.no>
* [ The author's description... ]jb1999-03-231-10/+30
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | o Runnable threads are now maintained in priority queues. The implementation requires two things: 1.) The priority queues must be protected during insertion and removal of threads. Since the kernel scheduler must modify the priority queues, a spinlock for protection cannot be used. The functions _thread_kern_sched_defer() and _thread_kern_sched_undefer() were added to {un}defer kernel scheduler activation. 2.) A thread (active) priority change can be performed only when the thread is removed from the priority queue. The implementation uses a threads active priority when inserting it into the queue. A by-product is that thread switches are much faster. A separate queue is used for waiting and/or blocked threads, and it is searched at most 2 times in the kernel scheduler when there are active threads. It should be possible to reduce this to once by combining polling of threads waiting on I/O with the loop that looks for timed out threads and the minimum timeout value. o Functions to defer kernel scheduler activation were added. These are _thread_kern_sched_defer() and _thread_kern_sched_undefer() and may be called recursively. These routines do not block the scheduling signal, but latch its occurrence. The signal handler will not call the kernel scheduler when the running thread has deferred scheduling, but it will be called when running thread undefers scheduling. o Added support for _POSIX_THREAD_PRIORITY_SCHEDULING. All the POSIX routines required by this should now be implemented. One note, SCHED_OTHER, SCHED_FIFO, and SCHED_RR are required to be defined by including pthread.h. These defines are currently in sched.h. I modified pthread.h to include sched.h but don't know if this is the proper thing to do. o Added support for priority protection and inheritence mutexes. This allows definition of _POSIX_THREAD_PRIO_PROTECT and _POSIX_THREAD_PRIO_INHERIT. o Added additional error checks required by POSIX for mutexes and condition variables. o Provided a wrapper for sigpending which is marked as a hidden syscall. o Added a non-portable function as a debugging aid to allow an application to monitor thread context switches. An application can install a routine that gets called everytime a thread (explicitly created by the application) gets context switched. The routine gets passed the pthread IDs of the threads that are being switched in and out. Submitted by: Dan Eischen <eischen@vigrid.com> Changes by me: o Added a PS_SPINBLOCK state to deal with the priority inversion problem most often (I think) seen by threads calling malloc/free/realloc. o Dispatch signals to the running thread directly rather than at a context switch to avoid the situation where the switch never occurs.
* Fix some bugs in pthread scheduler:dt1998-10-091-0/+3
| | | | | | | | make pthread_yield() more reliable, threads always (I hope) preempted at least every 0.1 sec, as intended. PR: bin/7744 Submitted by: "Richard Seaman, Jr." <dick@tar.com>
* Move the cleanup code that frees memory allocated for a dead thread fromjb1998-09-301-0/+16
| | | | | | | | | | | | | | the thread kernel into a garbage collector thread which is started when the fisrt thread is created (other than the initial thread). This removes the window of opportunity where a context switch will cause a thread that has locked the malloc spinlock, to enter the thread kernel, find there is a dead thread and try to free memory, therefore trying to lock the malloc spinlock against itself. The garbage collector thread acts just like any other thread, so instead of having a spinlock to control accesses to the dead thread list, it uses a mutex and a condition variable so that it can happily wait to be signalled when a thread exists.
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