On 06/11/2015 10:07 AM, Ingo Molnar wrote:
The memory hotplug code uses sync_global_pgds() to synchronize updates to the global (&init_mm) kernel PGD and the task PGDs. It does this by iterating over the pgd_list - which list closely tracks task creation/destruction via fork/clone.But we want to remove this list, so that it does not have to be maintained from fork()/exit(), so convert the memory hotplug code to use the task list to iterate over all pgds in the system. Also improve the comments a bit, to make this function easier to understand. Only lightly tested, as I don't have a memory hotplug setup. Cc: Andrew Morton<a...@linux-foundation.org> Cc: Andy Lutomirski<l...@amacapital.net> Cc: Borislav Petkov<b...@alien8.de> Cc: Brian Gerst<brge...@gmail.com> Cc: Denys Vlasenko<dvlas...@redhat.com> Cc: H. Peter Anvin<h...@zytor.com> Cc: Linus Torvalds<torva...@linux-foundation.org> Cc: Peter Zijlstra<pet...@infradead.org> Cc: Thomas Gleixner<t...@linutronix.de> Cc: Waiman Long<waiman.l...@hp.com> Signed-off-by: Ingo Molnar<mi...@kernel.org> --- arch/x86/mm/init_64.c | 30 +++++++++++++++++------------- 1 file changed, 17 insertions(+), 13 deletions(-) diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c index 3fba623e3ba5..1921acbd49fd 100644 --- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -160,8 +160,8 @@ static int __init nonx32_setup(char *str) __setup("noexec32=", nonx32_setup); /* - * When memory was added/removed make sure all the processes MM have - * suitable PGD entries in the local PGD level page. + * When memory was added/removed make sure all the process MMs have + * matching PGD entries in the local PGD level page as well. */ 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) { + pgd_t *pgd = p->mm->pgd; spinlock_t *pgt_lock; - pgd = (pgd_t *)page_address(page) + pgd_index(address); - /* the pgt_lock only for Xen */ - pgt_lock =&pgd_page_get_mm(page)->page_table_lock; + if (!p->mm) + continue;
pgd was initialized to p->mm->pgd before the "p->mm" check is done. Shouldn't the initialization be moved after that.
Cheers, Longman -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
