Messages in this thread | | | Date | Wed, 13 Aug 2008 13:07:49 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] kexec jump: fix compiling warning on xchg(&kexec_lock, 0) in kernel_kexec() |
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On Wed, 13 Aug 2008 12:50:57 -0700 (PDT) Linus Torvalds <torvalds@linux-foundation.org> wrote:
> > > On Wed, 13 Aug 2008, Andrew Morton wrote: > > - * in interrupt context :) > > + * Return true if we acquired the lock > > */ > > -static int kexec_lock; > > +static inline bool kexec_trylock(void) > > +{ > > + return !test_and_set_bit(0, &kexec_bitlock); > > Nope. That needs to be an "unsigned long".
It is.
> But more importantl, why not just make it a lock in the first place? > > static DEFINE_SPINLOCK(kexec_lock); > > #define kexec_trylock() spin_trylock(&kexec_lock) > #define kexec_unlock() spin_unlock(&kexec_lock) > > and then you get it all right and clear and obvious.
Used a bitop to preserve the runtime checking in there. spin_unlock() doesn't return the previous lockedness.
Presumably lockdep will whine about spun_unlock(unlocked_lock) though.
> Yeah, and I didn't check whether there is anything that is supposed to be > able to sleep. If there is, use a mutex instead of a spinlock, of course.
Yes, it does sleepy things inside the lock.
A bitop seems a better fit to me. We never spin on that lock (it always uses test_and_set), so why use a "spin"lock?
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