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2011-09-27process-shared barrier support, based on discussion with bdonlanRich Felker-16/+102
this implementation is rather heavy-weight, but it's the first solution i've found that's actually correct. all waiters actually wait twice at the barrier so that they can synchronize exit, and they hold a "vm lock" that prevents changes to virtual memory mappings (and blocks pthread_barrier_destroy) until all waiters are finished inspecting the barrier. thus, it is safe for any thread to destroy and/or unmap the barrier's memory as soon as pthread_barrier_wait returns, without further synchronization.
2011-09-27fix incorrect allocation failure check in pthread_createRich Felker-1/+1
mmap returns MAP_FAILED not 0 because some idiot thought the ability to mmap the null pointer page would be a good idea...
2011-09-26fix ctype macros to cast argument to (unsigned) firstRich Felker-7/+7
issue reported by nsz, but it's actually not just pedantic. the functions can take input of any arithmetic type, including floating point, and the behavior needs to be as if the conversion implicit in the function call took place.
2011-09-26another cond var fix: requeue count race conditionRich Felker-15/+13
lock out new waiters during the broadcast. otherwise the wait count added to the mutex might be lower than the actual number of waiters moved, and wakeups may be lost. this issue could also be solved by temporarily setting the mutex waiter count higher than any possible real count, then relying on the kernel to tell us how many waiters were requeued, and updating the counts afterwards. however the logic is more complex, and i don't really trust the kernel. the solution here is also nice in that it replaces some atomic cas loops with simple non-atomic ops under lock.
2011-09-26fix lost signals in cond varsRich Felker-14/+17
due to moving waiters from the cond var to the mutex in bcast, these waiters upon wakeup would steal slots in the count from newer waiters that had not yet been signaled, preventing the signal function from taking any action. to solve the problem, we simply use two separate waiter counts, and so that the original "total" waiters count is undisturbed by broadcast and still available for signal.
2011-09-26cleanup various minor issues reported by nszRich Felker-9/+9
the changes to syscall_ret are mostly no-ops in the generated code, just cleanup of type issues and removal of some implementation-defined behavior. the one exception is the change in the comparison value, which is fixed so that 0xf...f000 (which in principle could be a valid return value for mmap, although probably never in reality) is not treated as an error return.
2011-09-26redo cond vars again, use sequence numbersRich Felker-48/+52
testing revealed that the old implementation, while correct, was giving way too many spurious wakeups due to races changing the value of the condition futex. in a test program with 5 threads receiving broadcast signals, the number of returns from pthread_cond_wait was roughly 3 times what it should have been (2 spurious wakeups for every legitimate wakeup). moreover, the magnitude of this effect seems to grow with the number of threads. the old implementation may also have had some nasty race conditions with reuse of the cond var with a new mutex. the new implementation is based on incrementing a sequence number with each signal event. this sequence number has nothing to do with the number of threads intended to be woken; it's only used to provide a value for the futex wait to avoid deadlock. in theory there is a danger of race conditions due to the value wrapping around after 2^32 signals. it would be nice to eliminate that, if there's a way. testing showed no spurious wakeups (though they are of course possible) with the new implementation, as well as slightly improved performance.
2011-09-25revert previous change in cond var waiter moveRich Felker-2/+6
using swap has a race condition: the waiters must be added to the mutex waiter count *before* they are taken off the cond var waiter count, or wake events can be lost.
2011-09-25optimize cond waiter move using atomic swap instead of cas loopRich Felker-6/+2
2011-09-25fix logic for when wakeup is not desired on cond bcastRich Felker-3/+4
somehow i forgot that normal-type mutexes don't store the owner tid.
2011-09-25new futex-requeue-based pthread_cond_broadcast implementationRich Felker-7/+69
this avoids the "stampede effect" where pthread_cond_broadcast would result in all waiters waking up simultaneously, only to immediately contend for the mutex and go back to sleep.
2011-09-23fix ABA race in cond vars, improve them overallRich Felker-11/+12
previously, a waiter could miss the 1->0 transition of block if another thread set block to 1 again after the signal function set block to 0. we now use the caller's thread id as a unique token to store in block, which no other thread will ever write there. this ensures that if block still contains the tid, no signal has occurred. spurious wakeups will of course occur whenever there is a spurious return from the futex wait and another thread has begun waiting on the cond var. this should be a rare occurrence except perhaps in the presence of interrupting signal handlers. signal/bcast operations have been improved by noting that they need not avoid inspecting the cond var's memory after changing the futex value. because the standard allows spurious wakeups, there is no way for an application to distinguish between a spurious wakeup just before another thread called signal/bcast, and the deliberate wakeup resulting from the signal/bcast call. thus the woken thread must assume that the signalling thread may still be waiting to act on the cond var, and therefore it cannot destroy/unmap the cond var.
2011-09-23FD_ISSET must return an int. this is the easiest way.Rich Felker-1/+1
casting to int would not be correct because high bits could be lost. mapping the high bits down onto low bits would be costlier in the common case where the result is just used in a conditional. changing the type of the bit array elements to int would permute the order of the bit array on 64-bit big endian systems, so that's not an option either.
2011-09-23sys/user.h may need stdint.hRich Felker-0/+1
2011-09-22"optimize" arm __pthread_selfRich Felker-4/+1
actually this is just to avoid gcc being stupid and refusing to inline the function version, even when the size cost is essentially identical whether it's inlined or not.
2011-09-22fix deadlock in condition wait whenever there are multiple waitersRich Felker-5/+18
it's amazing none of the conformance tests i've run even bothered to check whether something so basic works...
2011-09-22fix x86_64 user.h (previously was just a copy of i386)Rich Felker-48/+13
2011-09-22cleanup/debloat i386 user.hRich Felker-43/+11
2011-09-22wrong __WORDSIZE in x86_64 headerRich Felker-1/+1
2011-09-21protect against/handle cancellation reading shadow passwordsRich Felker-1/+11
2011-09-21make dns lookups (and thus getaddrinfo) cancellableRich Felker-4/+11
2011-09-21use poll rather than select in dns lookups (also clock_gettime)Rich Felker-12/+10
if the file descriptor resource limit has been increased past FD_SETSIZE, this is actually a security issue; we could write past the end of the fd_set object. using poll makes it a non-issue, and simplifies the code at the same time. also, use clock_gettime instead of gettimeofday, for reduced bloat and better entropy.
2011-09-21fix missing SIG_DFL, SIG_IGN, SIG_ERR without posix in signal.hRich Felker-5/+6
2011-09-21avoid setting FILE lock count when not using flockfileRich Felker-1/+1
for now this is just a tiny optimization, but later if we support cancellation from __stdio_read and __stdio_write, it will be necessary for the recusrive lock count to be zero in order for these functions to know they are responsible for unlocking the FILE on cancellation.
2011-09-21gnu search.h has struct qelem...Rich Felker-0/+7
2011-09-21release notes for 0.8.3v0.8.3Rich Felker-0/+13
2011-09-21update syscalls with off_t arguments to handle argument alignment, if neededRich Felker-11/+14
the arm syscall abi requires 64-bit arguments to be aligned on an even register boundary. these new macros facilitate meeting the abi requirement without imposing significant ugliness on the code.
2011-09-21new gcc wrapper now supports pre-4.4 gcc versions and is more robustRich Felker-17/+40
2011-09-21new installation guide with alternate and primary libc setupsRich Felker-37/+107
2011-09-20fix some header typosRich Felker-2/+2
2011-09-20make stdbool.h conform to c99Rich Felker-1/+2
2011-09-20fix incorrect include guard in mqueue.hRich Felker-2/+2
2011-09-20fix statvfs.c to match new fsid_t definitionRich Felker-1/+1
2011-09-20fix the fsid_t structure to match name of __valRich Felker-1/+1
this is a case of poorly written man pages not matching the actual implementation, and why i hate implementing nonstandard interfaces with no actual documentation of how they're intended to work.
2011-09-20fix broken siginfo_t with _GNU_SOURCE definedRich Felker-6/+5
this bug was introduced in a recent patch. the problem we're working around is that broken GNU software wants to use "struct siginfo" rather than "siginfo_t", but "siginfo" is not in the reserved namespace and thus not legal for the standard header to use.
2011-09-19fix the definition of struct statvfs to match lsb abiRich Felker-70/+88
at the same time, make struct statfs match the traditional definition and make it more useful, especially the fsid_t stuff.
2011-09-19add some more siginfo aliases broken software expects...Rich Felker-0/+2
2011-09-19cleanup redundancy in bits/signal.h versionsRich Felker-376/+139
2011-09-19fix the type of wchar_t on arm; support wchar_t varying with archRich Felker-21/+20
really wchar_t should never vary, but the ARM EABI defines it as an unsigned 32-bit int instead of a signed one, and gcc follows this nonsense. thus, to give a conformant environment, we have to follow (otherwise L""[0] and L'\0' would be 0U rather than 0, but the application would be unaware due to a mismatched definition for WCHAR_MIN and WCHAR_MAX, and Bad Things could happen with respect to signed/unsigned comparisons, promotions, etc.). fortunately no rules are imposed by the C standard on the relationship between wchar_t and wint_t, and WEOF has type wint_t, so we can still make wint_t always-signed and use -1 for WEOF.
2011-09-19fix incorrect long double parameters on arm (and other future ports)Rich Felker-10/+22
this was the cause of crashes in printf when attempting to print floating point values.
2011-09-19fix broken multi-inclusion guard in sys/reg.hRich Felker-2/+2
2011-09-18initial commit of the arm portRich Felker-0/+2225
this port assumes eabi calling conventions, eabi linux syscall convention, and presence of the kernel helpers at 0xffff0f?0 needed for threads support. otherwise it makes very few assumptions, and the code should work even on armv4 without thumb support, as well as on systems with thumb interworking. the bits headers declare this a little endian system, but as far as i can tell the code should work equally well on big endian. some small details are probably broken; so far, testing has been limited to qemu/aboriginal linux.
2011-09-18disable dynamic linking/loading code in static libc builds, for nowRich Felker-0/+2
it does not work, but some configure scripts will falsely detect support then generate programs that crash when they call dlopen.
2011-09-18cleanup more bits cruft (sysmacros and socket)Rich Felker-414/+199
2011-09-18more bits junk (tcp.h)Rich Felker-3/+1
2011-09-18move invariant netinet/in.h stuff out of bits/in.hRich Felker-292/+147
2011-09-18overhaul clone syscall wrappingRich Felker-62/+135
several things are changed. first, i have removed the old __uniclone function signature and replaced it with the "standard" linux __clone/clone signature. this was necessary to expose clone to applications anyway, and it makes it easier to port __clone to new archs, since it's now testable independently of pthread_create. secondly, i have removed all references to the ugly ldt descriptor structure (i386 only) from the c code and pthread structure. in places where it is needed, it is now created on the stack just when it's needed, in assembly code. thus, the i386 __clone function takes the desired thread pointer as its argument, rather than an ldt descriptor pointer, just like on all other sane archs. this should not affect applications since there is really no way an application can use clone with threads/tls in a way that doesn't horribly conflict with and clobber the underlying implementation's use. applications are expected to use clone only for creating actual processes, possibly with new namespace features and whatnot.
2011-09-17release notes for 0.8.2v0.8.2Rich Felker-0/+11
2011-09-17dummy implementation of set_thread_areaRich Felker-0/+6
eventually we may have a working "generic" implementation for archs that don't need anything special. in any case, the goal of having stubs like this is to allow early testing of new ports before all the details needed for threads have been filled in. more functions like this will follow.
2011-09-16fix assumptions that char is signedRich Felker-2/+2