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* pthread_create need not set errnoRich Felker2011-04-031-1/+1
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* block all signals during rsyscallRich Felker2011-04-031-4/+9
| | | | | otherwise a signal handler could see an inconsistent and nonconformant program state where different threads have different uids/gids.
* fix race condition in rsyscall handlerRich Felker2011-04-031-1/+1
| | | | | | | | | | | | | | | | | | the problem: there is a (single-instruction) race condition window between a thread flagging itself dead and decrementing itself from the thread count. if it receives the rsyscall signal at this exact moment, the rsyscall caller will never succeed in signalling enough flags to succeed, and will deadlock forever. in previous versions of musl, the about-to-terminate thread masked all signals prior to decrementing the thread count, but this cost a whole syscall just to account for extremely rare races. the solution is a huge hack: rather than blocking in the signal handler if the thread is dead, modify the signal mask of the saved context and return in order to prevent further signal handling by the dead thread. this allows the dead thread to continue decrementing the thread count (if it had not yet done so) and exiting, even while the live part of the program blocks for rsyscall.
* don't trust siginfo in rsyscall handlerRich Felker2011-04-031-3/+2
| | | | | | | | for some inexplicable reason, linux allows the sender of realtime signals to spoof its identity. permission checks for sending signals should limit the impact to same-user processes, but just to be safe, we avoid trusting the siginfo structure and instead simply examine the program state to see if we're in the middle of a legitimate rsyscall.
* simplify calling of timer signal handlerRich Felker2011-04-031-7/+4
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* omit pthread tsd dtor code if tsd is not usedRich Felker2011-04-031-13/+6
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* simplify setting result on thread cancellationRich Felker2011-04-011-1/+1
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* fix misspelled PTHREAD_CANCELED constantRich Felker2011-04-011-1/+1
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* major improvements to cancellation handlingRich Felker2011-03-291-6/+12
| | | | | | | | | | | | | - there is no longer any risk of spoofing cancellation requests, since the cancel flag is set in pthread_cancel rather than in the signal handler. - cancellation signal is no longer unblocked when running the cancellation handlers. instead, pthread_create will cause any new threads created from a cancellation handler to unblock their own cancellation signal. - various tweaks in preparation for POSIX timer support.
* match glibc/lsb cancellation abi on i386Rich Felker2011-03-251-0/+5
| | | | | | | | glibc made the ridiculous choice to use pass-by-register calling convention for these functions, which is impossible to duplicate directly on non-gcc compilers. instead, we use ugly asm to wrap and convert the calling convention. presumably this works with every compiler anyone could potentially want to use.
* overhaul cancellation to fix resource leaks and dangerous behavior with signalsRich Felker2011-03-241-5/+11
| | | | | | | | | | | | | | | | | | | | | | | | | | | | this commit addresses two issues: 1. a race condition, whereby a cancellation request occurring after a syscall returned from kernelspace but before the subsequent CANCELPT_END would cause cancellable resource-allocating syscalls (like open) to leak resources. 2. signal handlers invoked while the thread was blocked at a cancellation point behaved as if asynchronous cancellation mode wer in effect, resulting in potentially dangerous state corruption if a cancellation request occurs. the glibc/nptl implementation of threads shares both of these issues. with this commit, both are fixed. however, cancellation points encountered in a signal handler will not be acted upon if the signal was received while the thread was already at a cancellation point. they will of course be acted upon after the signal handler returns, so in real-world usage where signal handlers quickly return, it should not be a problem. it's possible to solve this problem too by having sigaction() wrap all signal handlers with a function that uses a pthread_cleanup handler to catch cancellation, patch up the saved context, and return into the cancellable function that will catch and act upon the cancellation. however that would be a lot of complexity for minimal if any benefit...
* global cleanup to use the new syscall interfaceRich Felker2011-03-201-1/+1
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* syscall overhaul part two - unify public and internal syscall interfaceRich Felker2011-03-191-3/+3
| | | | | | | | | | | | | | | | with this patch, the syscallN() functions are no longer needed; a variadic syscall() macro allows syscalls with anywhere from 0 to 6 arguments to be made with a single macro name. also, manually casting each non-integer argument with (long) is no longer necessary; the casts are hidden in the macros. some source files which depended on being able to define the old macro SYSCALL_RETURNS_ERRNO have been modified to directly use __syscall() instead of syscall(). references to SYSCALL_SIGSET_SIZE and SYSCALL_LL have also been changed. x86_64 has not been tested, and may need a follow-up commit to fix any minor bugs/oversights.
* overhaul syscall interfaceRich Felker2011-03-191-2/+2
| | | | | | | | | | | | | | | this commit shuffles around the location of syscall definitions so that we can make a syscall() library function with both SYS_* and __NR_* style syscall names available to user applications, provides the syscall() library function, and optimizes the code that performs the actual inline syscalls in the library itself. previously on i386 when built as PIC (shared library), syscalls were incurring bus lock (lock prefix) overhead at entry and exit, due to the way the ebx register was being loaded (xchg instruction with a memory operand). now the xchg takes place between two registers. further cleanup to arch/$(ARCH)/syscall.h is planned.
* cut out a syscall on thread creation in the case where guard size is 0Rich Felker2011-03-161-1/+1
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* implement flockfile api, rework stdio lockingRich Felker2011-03-121-0/+1
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* optimize pthread termination in the non-detached caseRich Felker2011-03-101-4/+15
| | | | | | | we can avoid blocking signals by simply using a flag to mark that the thread has exited and prevent it from getting counted in the rsyscall signal-pingpong. this restores the original pthread create/join throughput from before the sigprocmask call was added.
* security fix: check that cancel/rsyscall signal was sent by the process itselfRich Felker2011-03-101-0/+3
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* use rt_sigprocmask, not legacy sigprocmask, syscall in pthread exit codeRich Felker2011-02-191-1/+1
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* race condition fix: block all signals before decrementing thread countRich Felker2011-02-191-0/+2
| | | | | | | | | | | | the existence of a (kernelspace) thread must never have observable effects after the thread count is decremented. if signals are not blocked, it could end up handling the signal for rsyscall and contributing towards the count of threads which have changed ids, causing a thread to be missed. this could lead to one thread retaining unwanted privilege level. this change may also address other subtle race conditions in application code that uses signals.
* make pthread_exit run dtors for last thread, wait to decrement thread countRich Felker2011-02-191-3/+3
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* reorganize pthread data structures and move the definitions to alltypes.hRich Felker2011-02-171-3/+3
| | | | | | | | this allows sys/types.h to provide the pthread types, as required by POSIX. this design also facilitates forcing ABI-compatible sizes in the arch-specific alltypes.h, while eliminating the need for developers changing the internals of the pthread types to poke around with arch-specific headers they may not be able to test.
* begin unifying clone/thread management interface in preparation for portingRich Felker2011-02-151-4/+2
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* make pthread_create return EAGAIN on resource failure, as required by POSIXRich Felker2011-02-151-1/+1
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* reorganize thread exit code, make pthread_exit call cancellation handlers (pt2)Rich Felker2011-02-131-13/+50
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* initial check-in, version 0.5.0 v0.5.0Rich Felker2011-02-121-0/+189