Sourceware Bugzilla – Full Text Bug Listing
|Summary:||Provide some parts of librt in libc as well|
|Product:||glibc||Reporter:||Adam Jackson <ajax>|
|Component:||nptl||Assignee:||Not yet assigned to anyone <unassigned>|
Description Adam Jackson 2012-06-27 14:59:55 UTC
librt links against libpthread, mostly because aio_* are implemented in threads instead of in the kernel AFAICT. This is unfortunate, because many libraries would like to use (for example) clock_gettime, but doing so pulls in pthreads. Now you have no choice but to hit the more expensive thread-safe paths, because your library can't know whether multiple threads actually exist, only whether the pthread symbols are non-zero. The complementary problem also exists for applications that are unthreaded: if they link against librt, pthread symbols will be non-zero, and any thread-safe library beneath that app now has to behave thread-safely. This is especially comic when reading the clock_gettime implementation, which goes out of its way to work correctly regardless of whether __pthread_clock_gettime is available. Ideally it would be possible to provide most of these symbols from libc directly (presumably versioned so the app requires a sufficiently new libc).