Messages in this thread | | | From | Linus Torvalds <> | Date | Sun, 19 Jun 2022 09:50:32 -0500 | Subject | Re: [GIT pull] locking/urgent for 5.19-rc3 |
| |
On Sun, Jun 19, 2022 at 8:12 AM Thomas Gleixner <tglx@linutronix.de> wrote: > > A RT fix for lockdep. lockdep invokes prandom_u32() to create cookies. This > worked until prandom_u32() was switched to the real random generator, which > takes a spinlock for extraction, which does not work on RT when invoked > from atomic contexts. lockdep has no requirement for real random numbers > and it turns out sched_clock() is good enough to create the cookie. That > works everywhere and is faster.
So this is obviously fine and works ok, but I do think it highlights that maybe that prandom change was a bad bad idea.
Even outside of RT, you might end up getting nasty locks within locks. Not a deadlock, but a "this was just pointless".
Linus
| |