path: root/src/thread
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2014-02-09clone: make clone a wrapper around __cloneBobby Bingham-18/+3
The architecture-specific assembly versions of clone did not set errno on failure, which is inconsistent with glibc. __clone still returns the error via its return value, and clone is now a wrapper that sets errno as needed. The public clone has also been moved to src/linux, as it's not directly related to the pthreads API. __clone is called by pthread_create, which does not report errors via errno. Though not strictly necessary, it's nice to avoid clobbering errno here.
2014-01-06eliminate explicit (long) casts when making syscallsRich Felker-1/+1
this practice came from very early, before internal/syscall.h defined macros that could accept pointer arguments directly and handle them correctly. aside from being ugly and unnecessary, it looks like it will be problematic when we add support for 32-bit ABIs on archs where registers (and syscall arguments) are 64-bit, e.g. x32 and mips n32.
2013-12-12include cleanups: remove unused headers and add feature test macrosSzabolcs Nagy-3/+0
2013-10-04fix invalid implicit pointer conversion in pthread_key_createRich Felker-1/+1
2013-09-20fix potential deadlock bug in libc-internal locking logicRich Felker-3/+6
if a multithreaded program became non-multithreaded (i.e. all other threads exited) while one thread held an internal lock, the remaining thread would fail to release the lock. the the program then became multithreaded again at a later time, any further attempts to obtain the lock would deadlock permanently. the underlying cause is that the value of libc.threads_minus_1 at unlock time might not match the value at lock time. one solution would be returning a flag to the caller indicating whether the lock was taken and needs to be unlocked, but there is a simpler solution: using the lock itself as such a flag. note that this flag is not needed anyway for correctness; if the lock is not held, the unlock code is harmless. however, the memory synchronization properties associated with a_store are costly on some archs, so it's best to avoid executing the unlock code when it is unnecessary.
2013-09-16fix clobbering of caller's stack in mips __clone functionRich Felker-0/+3
this was resulting in crashes in posix_spawn on mips, and would have affected applications calling clone too. since the prototype for __clone has it as a variadic function, it may not assume that 16($sp) is writable for use in making the syscall. instead, it needs to allocate additional stack space, and then adjust the stack pointer back in both of the code paths for the parent process/thread.
2013-09-16omit CLONE_PARENT flag to clone in pthread_createRich Felker-1/+1
CLONE_PARENT is not necessary (CLONE_THREAD provides all the useful parts of it) and Linux treats CLONE_PARENT as an error in certain situations, without noticing that it would be a no-op due to CLONE_THREAD. this error case prevents, for example, use of a multi-threaded init process and certain usages with containers.
2013-09-16use symbolic names for clone flags in pthread_createRich Felker-2/+5
2013-09-15support configurable page size on mips, powerpc and microblazeSzabolcs Nagy-0/+2
PAGE_SIZE was hardcoded to 4096, which is historically what most systems use, but on several archs it is a kernel config parameter, user space can only know it at execution time from the aux vector. PAGE_SIZE and PAGESIZE are not defined on archs where page size is a runtime parameter, applications should use sysconf(_SC_PAGE_SIZE) to query it. Internally libc code defines PAGE_SIZE to libc.page_size, which is set to aux[AT_PAGESZ] in __init_libc and early in __dynlink as well. (Note that libc.page_size can be accessed without GOT, ie. before relocations are done) Some fpathconf settings are hardcoded to 4096, these should be actually queried from the filesystem using statfs.
2013-09-14fix child stack alignment on mips cloneRich Felker-0/+1
unlike other archs, the mips version of clone was not doing anything to align the stack pointer. this seems to have been the cause for some SIGBUS crashes that were observed in posix_spawn.
2013-09-02fix mips-specific bug in synccall (too little space for signal mask)Rich Felker-5/+3
switch to the new __block_all_sigs/__restore_sigs internal API to clean up the code too.
2013-09-02in synccall, ignore the signal before any threads' signal handlers returnRich Felker-4/+4
this protects against deadlock from spurious signals (e.g. sent by another process) arriving after the controlling thread releases the other threads from the sync operation.
2013-09-02fix invalid pointer in synccall (multithread setuid, etc.)Rich Felker-0/+1
the head pointer was not being reset between calls to synccall, so any use of this interface more than once would build the linked list incorrectly, keeping the (now invalid) list nodes from the previous call.
2013-07-31in pthread_getattr_np, use mremap rather than madvise to measure stackRich Felker-1/+2
the original motivation for this patch was that qemu (and possibly other syscall emulators) nop out madvise, resulting in an infinite loop. however, there is another benefit to this change: madvise may actually undo an explicit madvise the application intended for its stack, whereas the mremap operation is a true nop. the logic here is that mremap must fail if it cannot resize the mapping in-place, and the caller knows that it cannot resize in-place because it knows the next page of virtual memory is already occupied.
2013-07-22make pthread attribute types structs, even when they just have one fieldRich Felker-22/+22
this change is to get the right tags for C++ ABI matching. it should have no other effects.
2013-06-26fix syscall argument bug in pthread_getschedparamRich Felker-1/+1
the address of the pointer to the sched param, rather than the pointer, was being passed to the kernel.
2013-06-26fix temp file leak in sem_open on successful creation of new semaphoreRich Felker-2/+2
2013-06-26fix bug whereby sem_open leaked its own internal slots on failureRich Felker-3/+6
2013-06-26in sem_open, don't leak vm mapping if fstat failsRich Felker-2/+2
fstat should not fail under normal circumstances, so this fix is mostly theoretical.
2013-06-26fix failure of pthread_setschedparam to pass correct param to kernelRich Felker-1/+1
the address of the pointer, rather than the pointer, was being passed. this was probably a copy-and-paste error from corresponding get code.
2013-06-08support cputime clocks for processes/threads other than selfRich Felker-1/+2
apparently these features have been in Linux for a while now, so it makes sense to support them. the bit twiddling seems utterly illogical and wasteful, especially the negation, but that's how the kernel folks chose to encode pids/tids into the clock id.
2013-06-03ensure that thread dtv pointer is never null to optimize __tls_get_addrRich Felker-0/+2
2013-04-26transition to using functions for internal signal blocking/restoringRich Felker-8/+5
there are several reasons for this change. one is getting rid of the repetition of the syscall signature all over the place. another is sharing the constant masks without costly GOT accesses in PIC. the main motivation, however, is accurately representing whether we want to block signals that might be handled by the application, or all signals.
2013-04-26prevent code from running under a thread id which already gave ESRCHRich Felker-1/+7
2013-04-26synccall signal handler need not handle dead threads anymoreRich Felker-9/+0
they have already blocked signals before decrementing the thread count, so the code being removed is unreachable in the case where the thread is no longer counted.
2013-04-26fix clobbering of signal mask when creating thread with sched attributesRich Felker-1/+1
this was simply a case of saving the state in the wrong place.
2013-04-26make last thread's pthread_exit give exit(0) a consistent stateRich Felker-3/+13
the previous few commits ended up leaving the thread count and signal mask wrong for atexit handlers and stdio cleanup.
2013-04-26use atomic decrement rather than cas in pthread_exit thread countRich Felker-4/+1
now that blocking signals prevents any application code from running while the last thread is exiting, the cas logic is no longer needed to prevent decrementing below zero.
2013-04-26add comments on some of the pthread_exit logicRich Felker-2/+15
2013-04-26always block signals in pthread_exit before decrementing thread countRich Felker-2/+2
the thread count (1+libc.threads_minus_1) must always be greater than or equal to the number of threads which could have application code running, even in an async-signal-safe sense. there is at least one dangerous race condition if this invariant fails to hold: dlopen could allocate too little TLS for existing threads, and a signal handler running in the exiting thread could claim the allocated TLS for itself (via __tls_get_addr), leaving too little for the other threads it was allocated for and thereby causing out-of-bounds access. there may be other situations where it's dangerous for the thread count to be too low, particularly in the case where only one thread should be left, in which case locking may be omitted. however, all such code paths seem to arise from undefined behavior, since async-signal-unsafe functions are not permitted to be called from a signal handler that interrupts pthread_exit (which is itself async-signal-unsafe). this change may also simplify logic in __synccall and improve the chances of making __synccall async-signal-safe.
2013-04-06fix type error in pthread_create, introduced with pthread_getattr_npRich Felker-1/+1
2013-03-31implement pthread_getattr_npRich Felker-2/+29
this function is mainly (purely?) for obtaining stack address information, but we also provide the detach state since it's easy to do anyway.
2013-03-26remove __SYSCALL_SSLEN arch macro in favor of using public _NSIGRich Felker-9/+9
the issue at hand is that many syscalls require as an argument the kernel-ABI size of sigset_t, intended to allow the kernel to switch to a larger sigset_t in the future. previously, each arch was defining this size in syscall_arch.h, which was redundant with the definition of _NSIG in bits/signal.h. as it's used in some not-quite-portable application code as well, _NSIG is much more likely to be recognized and understood immediately by someone reading the code, and it's also shorter and less cluttered. note that _NSIG is actually 65/129, not 64/128, but the division takes care of throwing away the off-by-one part.
2013-02-01fix stale locks left behind when pthread_create failsRich Felker-3/+6
this bug seems to have been around a long time.
2013-02-01if pthread_create fails, it must not attempt mmap if there is no mappingRich Felker-1/+1
this bug was introduced when support for application-provided stacks was originally added.
2013-02-01pthread stack treatment overhaul for application-provided stacks, etc.Rich Felker-23/+33
the main goal of these changes is to address the case where an application provides a stack of size N, but TLS has size M that's a significant portion of the size N (or even larger than N), thus giving the application less stack space than it expected or no stack at all! the new strategy pthread_create now uses is to only put TLS on the application-provided stack if TLS is smaller than 1/8 of the stack size or 2k, whichever is smaller. this ensures that the application always has "close enough" to what it requested, and the threshold is chosen heuristically to make sure "sane" amounts of TLS still end up in the application-provided stack. if TLS does not fit the above criteria, pthread_create uses mmap to obtain space for TLS, but still uses the application-provided stack for actual call frame stack. this is to avoid wasting memory, and for the sake of supporting ugly hacks like garbage collection based on assumptions that the implementation will use the provided stack range. in order for the above heuristics to ever succeed, the amount of TLS space wasted on POSIX TSD (pthread_key_create based) needed to be reduced. otherwise, these changes would preclude any use of pthread_create without mmap, which would have serious memory usage and performance costs for applications trying to create huge numbers of threads using pre-allocated stack space. the new value of PTHREAD_KEYS_MAX is the minimum allowed by POSIX, 128. this should still be plenty more than real-world applications need, especially now that C11/gcc-style TLS is now supported in musl, and most apps and libraries choose to use that instead of POSIX TSD when available. at the same time, PTHREAD_STACK_MIN has been decreased. it was originally set to PAGE_SIZE back when there was no support for TLS or application-provided stacks, and requests smaller than a whole page did not make sense. now, there are two good reasons to support requests smaller than a page: (1) applications could provide pre-allocated stacks smaller than a page, and (2) with smaller stack sizes, stack+TLS+TSD can all fit in one page, making it possible for applications which need huge numbers of threads with minimal stack needs to allocate exactly one page per thread. the new value of PTHREAD_STACK_MIN, 2k, is aligned with the minimum size for sigaltstack.
2013-02-01replace __wake function with macro that performs direct syscallRich Felker-9/+0
this should generate faster and smaller code, especially with inline syscalls. the conditional with cnt is ugly, but thankfully cnt is always a constant anyway so it gets evaluated at compile time. it may be preferable to make separate __wake and __wakeall macros without a count argument. priv flag is not used yet; private futex support still needs to be done at some point in the future.
2012-11-27fix some restrict-qualifier mismatches in newly added interfacesRich Felker-2/+2
these should have little/no practical impact but they're needed for strict conformance.
2012-11-19powerpc: handle syscall error in clone.rofl0r-25/+9
sigsetjmp: store temporaries in jmp_buf rather than on stack.
2012-11-18fix powerpc asm not to store data in volatile space below stack pointerRich Felker-4/+4
it's essential to decrement the stack pointer before writing to new stack space, rather than afterwards. otherwise there is a race condition during which asynchronous code (signals) could clobber the data being stored. it may be possible to optimize the code further using stwu, but I wanted to avoid making any changes to the actual stack layout in this commit. further improvements can be made separately if desired.
2012-11-17add stub versions of some missing optional pthread interfacesRich Felker-0/+30
priority inheritance is not yet supported, and priority protection probably will not be supported ever unless there's serious demand for it (it's a fairly heavy-weight feature). per-thread cpu clocks would be nice to have, but to my knowledge linux is still not capable of supporting them. glibc fakes them by using the _process_ cpu-time clock and subtracting the thread creation time, which gives seriously incorrect semantics (worse than not supporting the feature at all), so until there's a way to do it right, it will remain as a stub that always fails.
2012-11-14fix indention with spaces in powerpc asmRich Felker-8/+8
2012-11-14Merge remote-tracking branch 'ppc-port/ppc-squashed'Rich Felker-0/+154
2012-11-13PPC port cleaned up, static linking works well now.rofl0r-4/+147
2012-11-13import preliminary ppc work by rdp.Richard Pennington-0/+11
2012-11-11debloat src/thread tree but putting lots of junk in one fileRich Felker-108/+93
POSIX includes mostly-useless attribute-get functions for each attribute-set function, presumably out of some object-oriented dogmatism. the get functions are not useful with the simple idiomatic usage of attributes. there are of course possible valid uses of them (like writing wrappers for pthread init functions that perform special actions on the presence of certain attributes), but considering how tiny these functions are anyway, little is lost by putting them all in one file, and some build-time cost and archive-file-size benefits are achieved.
2012-11-11add support for thread scheduling (POSIX TPS option)Rich Felker-4/+106
linux's sched_* syscalls actually implement the TPS (thread scheduling) functionality, not the PS (process scheduling) functionality which the sched_* functions are supposed to have. omitting support for the PS option (and having the sched_* interfaces fail with ENOSYS rather than omitting them, since some broken software assumes they exist) seems to be the only conforming way to do this on linux.
2012-11-08clean up sloppy nested inclusion from pthread_impl.hRich Felker-8/+13
this mirrors the stdio_impl.h cleanup. one header which is not strictly needed, errno.h, is left in pthread_impl.h, because since pthread functions return their error codes rather than using errno, nearly every single pthread function needs the errno constants. in a few places, rather than bringing in string.h to use memset, the memset was replaced by direct assignment. this seems to generate much better code anyway, and makes many functions which were previously non-leaf functions into leaf functions (possibly eliminating a great deal of bloat on some platforms where non-leaf functions require ugly prologue and/or epilogue).
2012-10-19fix order of syscall args for microblaze clone syscallRich Felker-3/+2
with this commit, based on testing with patches to qemu which are not yet upstream,
2012-10-18ensure microblaze __set_thread_area returns successRich Felker-1/+2
since it did not set the return-value register, the caller could wrongly interpret this as failure.