Message 125369 - Python tracker (original) (raw)

Martin v. Löwis <martin@v.loewis.de> added the comment:

I wonder why reading from /dev/urandom has a loop in the first place, though - isn't it guaranteed that you can read as many bytes as you want in one go? This goes back to #934711, and apparently, even the original patch had the loop - for reasons that got never questioned.

I found surprising that a read from /dev/urandom would be uninterruptible, so I digged a little, and found this mail from 1998:

[patch] fix for urandom read(2) not interruptible http://marc.info/?l=bugtraq&m=91495921611500&w=2

"It's a bug in random.c that doesn' t check for signal pending inside the read(2) code, so you have no chance to kill the process via signals until the read(2) syscall is finished, and it could take a lot of time before return, if the buffer given to the read syscall is very big..."

I've had a quick look at the source code, and indeed, read(2) from /dev/urandom can now be interrupted by a signal, so looping seems to be justified.

---

nosy: +loewis status: pending -> open

---

Python tracker <report@bugs.python.org> <http://bugs.python.org/issue10824>

---