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* make internal declarations for flockfile tracking functions checkableRich Felker2018-09-121-2/+0
| | | | | | | logically these belong to the intersection of the stdio and pthread subsystems, and either place the declarations could go (stdio_impl.h or pthread_impl.h) requires a forward declaration for one of the argument types.
* refactor flockfile not to duplicate lock mechanism logicRich Felker2018-04-181-7/+4
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* fix stdio lock dependency on read-after-free not faultingRich Felker2018-04-181-1/+5
| | | | | | | 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.
* add proper fuxed-based locking for stdioRich Felker2011-07-301-2/+4
| | | | | | | | | | | | | | | | | | | | | | 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.
* clean up handling of thread/nothread mode, lockingRich Felker2011-04-171-4/+1
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* optimize file locking: avoid cache-polluting writes to global storageRich Felker2011-03-161-2/+4
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* implement flockfile api, rework stdio lockingRich Felker2011-03-121-0/+9