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* fix stdio lock dependency on read-after-free not faultingRich Felker2018-04-181-16/+13
| | | | | | | instead of using a waiters count, add a bit to the lock field indicating that the lock may have waiters. threads which obtain the lock after contending for it will perform a potentially-spurious wake when they release the lock.
* document self-synchronized destruction issue for stdio lockingRich Felker2012-12-101-0/+10
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* avoid setting FILE lock count when not using flockfileRich Felker2011-09-211-1/+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.
* add proper fuxed-based locking for stdioRich Felker2011-07-301-14/+12
| | | | | | | | | | | | | | | | | | | | | | previously, stdio used spinlocks, which would be unacceptable if we ever add support for thread priorities, and which yielded pathologically bad performance if an application attempted to use flockfile on a key file as a major/primary locking mechanism. i had held off on making this change for fear that it would hurt performance in the non-threaded case, but actually support for recursive locking had already inflicted that cost. by having the internal locking functions store a flag indicating whether they need to perform unlocking, rather than using the actual recursive lock counter, i was able to combine the conditionals at unlock time, eliminating any additional cost, and also avoid a nasty corner case where a huge number of calls to ftrylockfile could cause deadlock later at the point of internal locking. this commit also fixes some issues with usage of pthread_self conflicting with __attribute__((const)) which resulted in crashes with some compiler versions/optimizations, mainly in flockfile prior to pthread_create.
* reduce some ridiculously large spin countsRich Felker2011-05-061-1/+1
| | | | | | these should be tweaked according to testing. offhand i know 1000 is too low and 5000 is likely to be sufficiently high. consider trying to add futexes to file locking, too...
* debloat: use __syscall instead of syscall where possibleRich Felker2011-04-171-1/+1
| | | | | | don't waste time (and significant code size due to function call overhead!) setting errno when the result of a syscall does not matter or when it can't fail.
* revert some more spin optimizations that turned out to be pessimizationsRich Felker2011-03-281-1/+1
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* simplify and optimize FILE lock handlingRich Felker2011-03-241-6/+7
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* global cleanup to use the new syscall interfaceRich Felker2011-03-201-1/+1
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* implement flockfile api, rework stdio lockingRich Felker2011-03-121-0/+19