[Python-Dev] [Python-checkins] cpython: Backed out changeset 36f2e236c601: For some reason, rewinddir() doesn't work as (original) (raw)
Charles-François Natali neologix at free.fr
Mon Jan 9 09:23:30 CET 2012
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Can rewinddir() end up touching the filesystem to retrieve data? I noticed that your previous change (the one this checkin reverted) moved it outside the GIL release macros. It just resets a position count. (in glibc).
Actually, it also calls lseek() on the directory FD: http://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/rewinddir.c;hb=HEAD
But lseek() doesn't (normally) perform I/O, it just sets an offset in the kernel file structure: http://lxr.free-electrons.com/source/fs/read_write.c#L38
For example, it's not documented to return EINTR.
Now, one could imagine that the kernel could do some read-ahead or some other magic things when passed SEEK_DATA or SEEK_HOLE, but seeking at the beginning of a directory FD should be fast.
Anyway, I ended up reverting this change, because for some reason this broke OpenIndiana buildbots (maybe rewinddir() is a no-op before readdir() has been called?).
Cheers,
cf
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