- 21 8月, 2014 1 次提交
-
-
由 Rich Felker 提交于
unfortunately this needs to be able to vary by arch, because of a huge mess GCC made: the GCC definition, which became the ABI, depends on quirks in GCC's definition of __alignof__, which does not match the formal alignment of the type. GCC's __alignof__ unexpectedly exposes the an implementation detail, its "preferred alignment" for the type, rather than the formal/ABI alignment of the type, which it only actually uses in structures. on most archs the two values are the same, but on some (at least i386) the preferred alignment is greater than the ABI alignment. I considered using _Alignas(8) unconditionally, but on at least one arch (or1k), the alignment of max_align_t with GCC's definition is only 4 (even the "preferred alignment" for these types is only 4).
-
- 19 8月, 2014 1 次提交
-
-
由 Rich Felker 提交于
the main idea of the changes made is to have waiters wait directly on the "barrier" lock that was used to prevent them from making forward progress too early rather than first waiting on the atomic state value and then attempting to lock the barrier. in addition, adjustments to the mutex waiter count are optimized. previously, each waking waiter decremented the count (unless it was the first) then immediately incremented it again for the next waiter (unless it was the last). this was a roundabout was of achieving the equivalent of incrementing it once for the first waiter and decrementing it once for the last.
-
- 18 8月, 2014 2 次提交
-
-
由 Rich Felker 提交于
previously, wake order could be unpredictable: if a waiter happened to leave its futex wait on the state early, e.g. due to EAGAIN while restarting after a signal handler, it could acquire the mutex out of turn. handling this required ugly O(n) list walking in the unwait function and accounting to remove waiters that already woke from the list. with the new changes, the "barrier" locks in each waiter node are only unlocked in turn. in addition to simplifying the code, this seems to improve performance slightly, probably by reducing the number of accesses threads make to each other's stacks. as an additional benefit, unrecoverable mutex re-locking errors (mainly ENOTRECOVERABLE for robust mutexes) no longer need to be handled with deadlock; they can be reported to the caller, since the unlocking sequence makes it unnecessary to rely on the mutex to synchronize access to the waiter list.
-
由 Rich Felker 提交于
the immediate issue that was reported by Jens Gustedt and needed to be fixed was corruption of the cv/mutex waiter states when switching to using a new mutex with the cv after all waiters were unblocked but before they finished returning from the wait function. self-synchronized destruction was also handled poorly and may have had race conditions. and the use of sequence numbers for waking waiters admitted a theoretical missed-wakeup if the sequence number wrapped through the full 32-bit space. the new implementation is largely documented in the comments in the source. the basic principle is to use linked lists initially attached to the cv object, but detachable on signal/broadcast, made up of nodes residing in automatic storage (stack) on the threads that are waiting. this eliminates the need for waiters to access the cv object after they are signaled, and allows us to limit wakeup to one waiter at a time during broadcasts even when futex requeue cannot be used. performance is also greatly improved, roughly double some tests. basically nothing is changed in the process-shared cond var case, where this implementation does not work, since processes do not have access to one another's local storage.
-
- 17 8月, 2014 4 次提交
-
-
由 Rich Felker 提交于
when the kernel is responsible for waking waiters on a robust mutex whose owner died, it does not have a waiters count available and must rely entirely on the waiter bit of the lock value. normally, this bit is only set by newly arriving waiters, so it will be clear if no new waiters arrived after the current owner obtained the lock, even if there are other waiters present. leaving it clear is desirable because it allows timed-lock operations to remove themselves as waiters and avoid causing unnecessary futex wake syscalls. however, for process-shared robust mutexes, we need to set the bit whenever there are existing waiters so that the kernel will know to wake them. for non-process-shared robust mutexes, the wake happens in userspace and can look at the waiters count, so the bit does not need to be set in the non-process-shared case.
-
由 Rich Felker 提交于
when manipulating the robust list, the order of stores matters, because the code may be asynchronously interrupted by a fatal signal and the kernel will then access the robust list in what is essentially an async-signal context. previously, aliasing considerations made it seem unlikely that a compiler could reorder the stores, but proving that they could not be reordered incorrectly would have been extremely difficult. instead I've opted to make all the pointers used as part of the robust list, including those in the robust list head and in the individual mutexes, volatile. in addition, the format of the robust list has been changed to point back to the head at the end, rather than ending with a null pointer. this is to match the documented kernel robust list ABI. the null pointer, which was previously used, only worked because faults during access terminate the robust list processing.
-
由 Rich Felker 提交于
a robust mutex should not enter the unrecoverable status until it's unlocked without marking it consistent. previously, flag 8 in the type was used as an indication of unrecoverable, but only honored after successful locking; this resulted in a race window where the unrecoverable mutex could appear to a second thread as locked/busy again while the first thread was in the process of observing it as unrecoverable. now, flag 8 is used to mean that the mutex is in the process of being recovered, but not yet marked consistent. the flag only takes effect in pthread_mutex_unlock, where it causes the value 0x40000000 (owner dead flag, with old owner tid 0, an otherwise impossible state) to be stored in the lock. subsequent lock attempts will interpret this state as unrecoverable.
-
由 Rich Felker 提交于
per the resolution of Austin Group issue 755, the POSIX requirement that ownership be enforced for recursive and error-checking mutexes does not allow a random new thread to acquire ownership of an orphaned mutex just because it happened to be assigned the same tid as the original owner that exited with the mutex locked. one possible fix for this issue would be to disallow the kernel thread to terminate when it exited with mutexes held, permanently reserving the tid against reuse. however, this does not solve the problem for process-shared mutexes where lifetime cannot be controlled, so it was not used. the alternate approach I've taken is to reuse the robust mutex system for non-robust recursive and error-checking mutexes. when a thread exits, the kernel (or the new userspace robust-list code added in commit b092f1c5) will set the owner-died bit for these orphaned mutexes, but since the mutex-type is not robust, pthread_mutex_trylock will not allow a new owner to acquire them. instead, they remain in a state of being permanently locked, as desired.
-
- 16 8月, 2014 3 次提交
-
-
由 Rich Felker 提交于
the whole point of this locking is to prevent munmap, or mmap with MAP_FIXED, from deallocating virtual addresses, or changing the backing a given virtual address refers to, during certain race windows involving self-synchronized unmapping or destruction of pthread synchronization objects. there is no need for exclusion in the other direction, so it suffices to take the lock momentarily and release it before making the syscall, rather than holding it across the syscall.
-
由 Rich Felker 提交于
the kernel always uses non-private wake when walking the robust list when a thread or process exits, so it's not able to wake waiters listening with the private futex flag. this problem is solved by doing the equivalent in userspace as the last step of pthread_exit. care is taken to remove mutexes from the robust list before unlocking them so that the kernel will not attempt to access them again, possibly after another thread locks them. this removal code can treat the list as singly-linked, since no further code which would add or remove items is able to run at this point. moreover, the pending pointer is not needed since the mutexes being unlocked are all process-local; in the case of asynchronous process termination, they all cease to exist. since a process-local robust mutex cannot come into existence without a call to pthread_mutexattr_setrobust in the same process, the code for userspace robust list processing is put in that source file, and a weak alias to a dummy function is used to avoid pulling in this bloat as part of pthread_exit in static-linked programs.
-
由 Rich Felker 提交于
private-futex uses the virtual address of the futex int directly as the hash key rather than requiring the kernel to resolve the address to an underlying backing for the mapping in which it lies. for certain usage patterns it improves performance significantly. in many places, the code using futex __wake and __wait operations was already passing a correct fixed zero or nonzero flag for the priv argument, so no change was needed at the site of the call, only in the __wake and __wait functions themselves. in other places, especially where the process-shared attribute for a synchronization object was not previously tracked, additional new code is needed. for mutexes, the only place to store the flag is in the type field, so additional bit masking logic is needed for accessing the type. for non-process-shared condition variable broadcasts, the futex requeue operation is unable to requeue from a private futex to a process-shared one in the mutex structure, so requeue is simply disabled in this case by waking all waiters. for robust mutexes, the kernel always performs a non-private wake when the owner dies. in order not to introduce a behavioral regression in non-process-shared robust mutexes (when the owning thread dies), they are simply forced to be treated as process-shared for now, giving correct behavior at the expense of performance. this can be fixed by adding explicit code to pthread_exit to do the right thing for non-shared robust mutexes in userspace rather than relying on the kernel to do it, and will be fixed in this way later. since not all supported kernels have private futex support, the new code detects EINVAL from the futex syscall and falls back to making the call without the private flag. no attempt to cache the result is made; caching it and using the cached value efficiently is somewhat difficult, and not worth the complexity when the benefits would be seen only on ancient kernels which have numerous other limitations and bugs anyway.
-
- 13 8月, 2014 3 次提交
-
-
由 Szabolcs Nagy 提交于
C99 6.10.3p11 disallows such constructs so use an #ifdef outside of the argument list of __syscall
-
由 Szabolcs Nagy 提交于
-
由 Szabolcs Nagy 提交于
isspace can be a bottleneck in a simple parser, inlining it gives slightly smaller and faster code src/locale/pleval.o already had this optimization, the size change for other libc functions for i386 is src/internal/intscan.o 2134 2118 -16 src/locale/dcngettext.o 1562 1552 -10 src/network/res_msend.o 1961 1940 -21 src/network/lookup_name.o 2627 2608 -19 src/network/getnameinfo.o 1814 1811 -3 src/network/lookup_serv.o 643 624 -19 src/stdio/vfscanf.o 2675 2663 -12 src/stdlib/atoll.o 117 107 -10 src/stdlib/atoi.o 95 91 -4 src/stdlib/atol.o 95 91 -4 src/time/strptime.o 1515 1503 -12 (TOTALS) 432451 432321 -130
-
- 08 8月, 2014 4 次提交
-
-
由 Rich Felker 提交于
-
由 Clément Vasseur 提交于
when the dynamic loader is disabled, dlopen fails correctly but dlerror did not return a human readable error string like it should have.
-
由 Clément Vasseur 提交于
glibc declares clearenv under _BSD_SOURCE, some applications might depend on it being available this way.
-
由 Timo Teräs 提交于
The function originates from SunOS 4.x in which the null argument is allowed. glibc also handles this case.
-
- 01 8月, 2014 4 次提交
-
-
由 Rich Felker 提交于
-
由 Rich Felker 提交于
-
由 Rich Felker 提交于
-
由 Rich Felker 提交于
the code which loads locale files was already rejecting locale names containing slashes. however, LC_MESSAGES records a locale name even if libc does not have a matching locale file, so that gettext or application code can use the recorded locale name for message translations to languages that libc does not support. this recorded name was not being checked for slashes, meaning that such code could potentially be tricked into directory traversal. in addition, since the value of a locale category is sometimes used as a pathname component by callers, the improved code rejects any value beginning with a dot. this prevents traversal to the parent directory via "..", use of the top-level locale directory via ".", and also avoids "hidden" directories as a side effect. finally, overly long locale names are now rejected (treated as an unrecognized name and thus as an alias for C.UTF-8) rather than being truncated.
-
- 31 7月, 2014 6 次提交
-
-
由 Rich Felker 提交于
per the resolution of Austin Group issue #617, these are accepted for XSI option in POSIX future and thus I'm treating them as standard functions.
-
由 Rich Felker 提交于
per the standard, ffs is XSI shaded, whereas the other functions in this header are in the base.
-
由 Rich Felker 提交于
for or1k, the kernel expects the offset passed to mmap2 in units of the 8k page size, not the standard unit of 4k used on most other archs.
-
由 Rich Felker 提交于
-
由 Rich Felker 提交于
according to Stefan Kristiansson, or1k page size is not actually variable and the value of 8192 is part of the ABI.
-
由 Szabolcs Nagy 提交于
using an operator precedence parser the code size became smaller and it is only slower by about %10 size of old vs new pleval.o on different archs: (with inlined isspace added to pleval.c for now) old: text data bss dec hex filename 828 0 0 828 33c pl.i386.o 1152 0 0 1152 480 pl.arm.o 1704 0 0 1704 6a8 pl.mips.o 1328 0 0 1328 530 pl.ppc.o 992 0 0 992 3e0 pl.x64.o new: text data bss dec hex filename 693 0 0 693 2b5 pl.i386.o 972 0 0 972 3cc pl.arm.o 1276 0 0 1276 4fc pl.mips.o 1087 0 0 1087 43f pl.ppc.o 846 0 0 846 34e pl.x64.o
-
- 30 7月, 2014 4 次提交
-
-
由 Timo Teräs 提交于
the previous implementations had several deficiencies, the most severe of which was the inability to report unconfigured interfaces or interfaces without ipv4 addresses. among the options discussed for fixing this, using netlink turned out to be the one with the least cost and most additional advantages. other improvements include: if_nameindex now avoids duplicates in the list it produces, but still includes legacy-style interface aliases if any are in use. getifaddrs now reports hardware addresses and includes the scope_id for link-local ipv6 addresses in the resulting address.
-
由 Rich Felker 提交于
this commit changes the names to match the kernel names, exposing under the normal names the "old" versions which work with a smaller termios structure compatible with the userspace structure, and renaming the "new" versions with "2" on the end like the kernel has. this fixes spurious warnings "Unsupported ioctl: cmd=0x802c542a" from qemu-sh4 and should be more correct anyway, since our userspace termios structure does not have meaningful information in the part which the kernel would be interpreting as speeds with the new ioctl.
-
由 Szabolcs Nagy 提交于
const parsing, depth accounting and failure handling was changed a bit so the generated code is slightly smaller.
-
由 Rich Felker 提交于
while the __mo_lookup backend can verify that the translated message ends with a null terminator, is has no way to know nplurals and thus no way to verify that sufficiently many null terminators are present in the string to satisfy all plural forms. the code in dcngettext was already attempting to avoid reading past the end of the mo file mapping, but failed to do so because the strlen call itself could over-read. using strnlen instead allows us to avoid the problem.
-
- 29 7月, 2014 2 次提交
-
-
由 Rich Felker 提交于
rather than just checking that the start of the string lies within the mapping, also check that the nominal length remains within the mapping, and that the null terminator is present at the nominal length. this ensures that the caller, using the result as a C string, will not read past the end of the mapping. the nominal length is never exposed to the caller, but it's useful internally to find where the null terminator should be without having to restort to linear search via strnlen/memchr.
-
由 Rich Felker 提交于
the new code in dcngettext was written by me, and the expression evaluator by Szabolcs Nagy (nsz).
-
- 28 7月, 2014 3 次提交
-
-
由 Rich Felker 提交于
this follows the same logic as in the previous commit for other archs.
-
由 Rich Felker 提交于
the a_cas_l, a_swap_l, a_swap_p, and a_store_l operations were probably used a long time ago when only i386 and x86_64 were supported. as other archs were added, support for them was inconsistent, and they are obviously not in use at present. having them around potentially confuses readers working on new ports, and the type-punning hacks and inconsistent use of types in their definitions is not a style I wish to perpetuate in the source tree, so removing them seems appropriate.
-
由 Rich Felker 提交于
while other usage I've seen only has the synco instruction after the atomic operation, I cannot find any documentation indicating that this is correct. certainly all stores before the atomic need to have been synchronized before the atomic operation takes place.
-
- 27 7月, 2014 1 次提交
-
-
由 Rich Felker 提交于
this commit replaces the stub implementations with working message translation functions. translation units are factored so as to prevent pulling in the legacy, non-library-safe functions which use a global textdomain in modern code which is using the versions with an explicit domain argument. bind_textdomain_codeset is also placed in its own file since it should not be needed by most programs. this implementation is still missing some features: the LANGUAGE environment variable (for multiple fallback languages) is not honored, and non-default plural-form rules are not supported. these issues will be addressed in a later commit. one notable difference from the GNU implementation is that there is no default path for loading translation files. in principle one could be added, but since the documented correct usage is to call the bindtextdomain function, a default path is probably unnecessary.
-
- 26 7月, 2014 2 次提交
-
-
由 Rich Felker 提交于
for LC_MESSAGES, translation of strerror and similar literal message functions is supported. for messages in other places (particularly the dynamic linker) that use format strings, translation is not yet supported. in order to make it possible and safe, such messages will need to be refactored to separate the textual content from the format. for LC_TIME, the day and month names and strftime-style format strings provided by nl_langinfo are supported for translation. however there may be limitations, as some of the original C-locale nl_langinfo strings are non-unique and thus perhaps non-suitable as keys. overall, the locale support activated by this commit should not be seen as complete and polished but as a basis for beginning to test locale functionality and implement locales.
-
由 Rich Felker 提交于
these were removed from the standard but still offered as an extension in langinfo.h, so nl_langinfo should support them.
-