On 06/11, Ingo Molnar wrote:
>
> void sync_global_pgds(unsigned long start, unsigned long end, int removed)
> {
> @@ -169,29 +169,33 @@ void sync_global_pgds(unsigned long start, unsigned
> long end, int removed)
>
> for (address = start; address <= end; address += PGDIR_SIZE) {
> const pgd_t *pgd_ref = pgd_offset_k(address);
> - struct page *page;
> + struct task_struct *g, *p;
>
> /*
> - * When it is called after memory hot remove, pgd_none()
> - * returns true. In this case (removed == 1), we must clear
> - * the PGD entries in the local PGD level page.
> + * When this function is called after memory hot remove,
> + * pgd_none() already returns true, but only the reference
> + * kernel PGD has been cleared, not the process PGDs.
> + *
> + * So clear the affected entries in every process PGD as well:
> */
> if (pgd_none(*pgd_ref) && !removed)
> continue;
>
> spin_lock(&pgd_lock);
> - list_for_each_entry(page, &pgd_list, lru) {
> - pgd_t *pgd;
> +
> + for_each_process_thread(g, p) {
Well, this looks obvously unsafe without rcu_read_lock() at least.
The usage of ->mm doesn't look safe too but this is fixeable, see
my previous reply to 7/12.
And probably I am totally confused, but it seems that 06/12 should
come before this patch? Otherwise, why we can't race with fork() and
miss the new process?
Oleg.
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