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332633 |
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16-Apr-2018 |
jhb |
MFC 331324: Ensure thread library is initialized in pthread_testcancel().
Call _thr_check_init() before reading curthread in pthread_testcancel().
If a constructor in a library creates a semaphore via sem_init() and then waits for it via sem_wait(), the program can core dump in _pthread_testcancel() called from sem_wait(). This is because the semaphore implementation lives in libc, so the library's constructors can be run before libthr's constructors.
Sponsored by: DARPA / AFRL
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256281 |
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10-Oct-2013 |
gjb |
Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.
Approved by: re (implicit) Sponsored by: The FreeBSD Foundation |
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251985 |
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19-Jun-2013 |
kib |
The SUSv4tc1 requires that pthread_setcancelstate() shall be not a cancellation point. When enabling the cancellation, only process the pending cancellation for asynchronous mode.
Reported and reviewed by: Kohji Okuno <okuno.kohji@jp.panasonic.com> Sponsored by: The FreeBSD Foundation MFC after: 1 week
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213153 |
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24-Sep-2010 |
davidxu |
To support stack unwinding for cancellation points, add -fexceptions flag for them, two functions _pthread_cancel_enter and _pthread_cancel_leave are added to let thread enter and leave a cancellation point, it also makes it possible that other functions can be cancellation points in libraries without having to be rewritten in libthr.
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213100 |
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24-Sep-2010 |
davidxu |
inline testcancel() into thr_cancel_leave(), because cancel_pending is almost false, this makes a slight better branch predicting.
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213096 |
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24-Sep-2010 |
davidxu |
In most cases, cancel_point and cancel_async needn't be checked again, because cancellation is almostly checked at cancellation points.
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212536 |
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13-Sep-2010 |
davidxu |
Convert thread list lock from mutex to rwlock.
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212312 |
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08-Sep-2010 |
davidxu |
To avoid possible race condition, SIGCANCEL is always sent except the thread is dead.
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212076 |
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01-Sep-2010 |
davidxu |
Add signal handler wrapper, the reason to add it becauses there are some cases we want to improve: 1) if a thread signal got a signal while in cancellation point, it is possible the TDP_WAKEUP may be eaten by signal handler if the handler called some interruptibly system calls. 2) In signal handler, we want to disable cancellation. 3) When thread holding some low level locks, it is better to disable signal, those code need not to worry reentrancy, sigprocmask system call is avoided because it is a bit expensive. The signal handler wrapper works in this way: 1) libthr installs its signal handler if user code invokes sigaction to install its handler, the user handler is recorded in internal array. 2) when a signal is delivered, libthr's signal handler is invoke, libthr checks if thread holds some low level lock or is in critical region, if it is true, the signal is buffered, and all signals are masked, once the thread leaves critical region, correct signal mask is restored and buffered signal is processed. 3) before user signal handler is invoked, cancellation is temporarily disabled, after user signal handler is returned, cancellation state is restored, and pending cancellation is rescheduled.
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211524 |
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20-Aug-2010 |
davidxu |
In current implementation, thread cancellation is done in signal handler, which does not know what is the state of interrupted system call, for example, open() system call opened a file and the thread is still cancelled, result is descriptor leak, there are other problems which can cause resource leak or undeterminable side effect when a thread is cancelled. However, this is no longer true in new implementation.
In defering mode, a thread is canceled if cancellation request is pending and later the thread enters a cancellation point, otherwise, a later pthread_cancel() just causes SIGCANCEL to be sent to the target thread, and causes target thread to abort system call, userland code in libthr then checks cancellation state, and cancels the thread if needed. For example, the cancellation point open(), the thread may be canceled at start, but later, if it opened a file descriptor, it is not canceled, this avoids file handle leak. Another example is read(), a thread may be canceled at start of the function, but later, if it read some bytes from a socket, the thread is not canceled, the caller then can decide if it should still enable cancelling or disable it and continue reading data until it thinks it has read all bytes of a packet, and keeps a protocol stream in health state, if user ignores partly reading of a packet without disabling cancellation, then second iteration of read loop cause the thread to be cancelled. An exception is that the close() cancellation point always closes a file handle despite whether the thread is cancelled or not.
The old mechanism is still kept, for a functions which is not so easily to fix a cancellation problem, the rough mechanism is used.
Reviewed by: kib@
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164896 |
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05-Dec-2006 |
davidxu |
Tweak _thr_cancel_leave_defer a bit to fix a possible race.
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164877 |
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04-Dec-2006 |
davidxu |
Use kernel provided userspace condition variable to implement pthread condition variable.
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164583 |
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24-Nov-2006 |
davidxu |
Eliminate atomic operations in thread cancellation functions, it should reduce overheads of cancellation points.
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157457 |
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04-Apr-2006 |
davidxu |
WARNS level 4 cleanup.
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157116 |
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25-Mar-2006 |
davidxu |
Don't cancel thread if it is in critical region.
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144518 |
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01-Apr-2005 |
davidxu |
Import my recent 1:1 threading working. some features improved includes: 1. fast simple type mutex. 2. __thread tls works. 3. asynchronous cancellation works ( using signal ). 4. thread synchronization is fully based on umtx, mainly, condition variable and other synchronization objects were rewritten by using umtx directly. those objects can be shared between processes via shared memory, it has to change ABI which does not happen yet. 5. default stack size is increased to 1M on 32 bits platform, 2M for 64 bits platform. As the result, some mysql super-smack benchmarks show performance is improved massivly.
Okayed by: jeff, mtm, rwatson, scottl
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129484 |
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20-May-2004 |
mtm |
Make libthr async-signal-safe without costly signal masking. The guidlines I followed are: Only 3 functions (pthread_cancel, pthread_setcancelstate, pthread_setcanceltype) are required to be async-signal-safe by POSIX. None of the rest of the pthread api is required to be async-signal-safe. This means that only the three mentioned functions are safe to use from inside signal handlers. However, there are certain system/libc calls that are cancellation points that a caller may call from within a signal handler, and since they are cancellation points calls have to be made into libthr to test for cancellation and exit the thread if necessary. So, the cancellation test and thread exit code paths must be async-signal-safe as well. A summary of the changes follows:
o Almost all of the code paths that masked signals, as well as locking the pthread structure now lock only the pthread structure. o Signals are masked (and left that way) as soon as a thread enters pthread_exit(). o The active and dead threads locks now explicitly require that signals are masked. o Access to the isdead field of the pthread structure is protected by both the active and dead list locks for writing. Either one is sufficient for reading. o The thread state and type fields have been combined into one three-state switch to make it easier to read without requiring a lock. It doesn't need a lock for writing (and therefore for reading either) because only the current thread can write to it and it is an integer value. o The thread state field of the pthread structure has been eliminated. It was an unnecessary field that mostly duplicated the flags field, but required additional locking that would make a lot more code paths require signal masking. Any truly unique values (such as PS_DEAD) have been reborn as separate members of the pthread structure. o Since the mutex and condvar pthread functions are not async-signal-safe there is no need to muck about with the wait queues when handling a signal ... o ... which also removes the need for wrapping signal handlers and sigaction(2). o The condvar and mutex async-cancellation code had to be revised as a result of some of these changes, which resulted in semi-unrelated changes which would have been difficult to work on as a separate commit, so they are included as well.
The only part of the changes I am worried about is related to locking for the pthread joining fields. But, I will take a closer look at them once this mega-patch is committed.
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126000 |
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19-Feb-2004 |
mtm |
Implement PThreads barriers and barrier attributes.
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117277 |
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06-Jul-2003 |
mtm |
Change all instances of THR_LOCK/UNLOCK, etc to UMTX_*. It is a more acurate description of the locks they operate on.
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117276 |
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06-Jul-2003 |
mtm |
There's no need for _umtxtrylock to be a separate function. Roll it into the pre-existing macro that's used to call it.
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117049 |
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29-Jun-2003 |
mtm |
Sweep through pthread locking and use the new locking primitives for libthr.
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115307 |
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25-May-2003 |
mtm |
_pthread_cancel() breaks the normal lock order of first locking the joined and then the joiner thread. There isn't an easy (sane?) way to make it use the correct order without introducing races involving the target thread and finding which (active or dead) list it is on. So, after locking the canceled thread it will try to lock the joined thread and if it fails release the first lock and try again from the top.
Introduce a new function, _spintrylock, which is simply a wrapper arround umtx_trylock(), to help accomplish this.
Approved by: re/blanket libthr
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115260 |
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23-May-2003 |
mtm |
Make WARNS2 clean. The fixes mostly included: o removed unused variables o explicit inclusion of header files o prototypes for externally defined functions
Approved by: re/blanket libthr
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115033 |
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15-May-2003 |
mtm |
o Make the setting/checking of cancel state atomic with respect to other threads and signal handlers by moving to the _thread_critical_enter/exit functions.
o Introduce an static function, testcancel(), that is used by the other functions in this module. This allows it to make locking assumptions that the top-level functions can't.
o Rework the code flow a bit to reduce indentation levels.
Approved by: markm/mentor, re/blanket libthr Reviewed by: jeff
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112965 |
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02-Apr-2003 |
jeff |
- Define curthread as _get_curthread() and remove all direct calls to _get_curthread(). This is similar to the kernel's curthread. Doing this saves stack overhead and is more convenient to the programmer. - Pass the pointer to the newly created thread to _thread_init(). - Remove _get_curthread_slow().
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112918 |
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01-Apr-2003 |
jeff |
- Add libthr but don't hook it up to the regular build yet. This is an adaptation of libc_r for the thr system call interface. This is beta quality code.
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