On Sat, 4 Jul 2020 at 12:30, Philippe Mathieu-Daudé <f4...@amsat.org> wrote: > Any idea what means TFR? I understand it keeps retrying while > interrupted, but can't find the origin of that abbreviation.
Probably it stands for "temporary failure retry" -- glibc provides essentially the same primitive in unistd.h as TEMP_FAILURE_RETRY: https://www.gnu.org/software/libc/manual/html_node/Interrupted-Primitives.html TFR is pretty old as QEMU code goes: added in commit aeb30be60a92148e38d in 2007. > I'm not sure what we gain by using this macro, it seems dangerous > as there is no guaranty we 'expr' is a single libc call updating > errno. Well, the design of the macro is that it is for use to wrap expressions which are a single thing that update errno... The gain overall is that "we need to retry practically everything to handle EINTR" results in lots of awkward open-coded loops, and in theory putting them behind macros makes the normal-case handling more obvious. But this only works if the codebase is going to consistently adopt TFR() as its EINTR-handling strategy. (EINTR is one of the big failures of the Unix/POSIX API, in my view.) thanks -- PMM
