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SubjectRe: [PATCH] [1/2] random: SMP locking
Oliver Xymoron <oxymoron@waste.org> wrote:
>
> This patch adds locking for SMP. Apparently Willy never managed to
> revive his laptop with his version so I revived mine.

hrm. I'm a random ignoramus. I'll look it over...

Are you really sure that all the decisions about where to use spin_lock()
vs spin_lock_irq() vs spin_lock_irqsave() are correct? They are
non-obvious.

> @@ -1619,18 +1660,23 @@
> if (!capable(CAP_SYS_ADMIN))
> return -EPERM;
> p = (int *) arg;
> + spin_lock(&random_state->lock);
> ent_count = random_state->entropy_count;
> if (put_user(ent_count, p++) ||
> get_user(size, p) ||
> put_user(random_state->poolinfo.poolwords, p++))

Cannot perform userspace access while holding a lock - a pagefault could
occur, perform IO, schedule away and the same CPU tries to take the same
lock via a different process.

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