From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f179.google.com (mail-wi0-f179.google.com [209.85.212.179]) by kanga.kvack.org (Postfix) with ESMTP id D4BE16B006E for ; Sat, 13 Jun 2015 05:49:35 -0400 (EDT) Received: by wibdq8 with SMTP id dq8so34970048wib.1 for ; Sat, 13 Jun 2015 02:49:35 -0700 (PDT) Received: from mail-wg0-x232.google.com (mail-wg0-x232.google.com. [2a00:1450:400c:c00::232]) by mx.google.com with ESMTPS id am6si11647576wjc.37.2015.06.13.02.49.34 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 13 Jun 2015 02:49:34 -0700 (PDT) Received: by wgv5 with SMTP id 5so37648548wgv.1 for ; Sat, 13 Jun 2015 02:49:34 -0700 (PDT) From: Ingo Molnar Subject: [PATCH 02/12] x86/mm/hotplug: Remove pgd_list use from the memory hotplug code Date: Sat, 13 Jun 2015 11:49:05 +0200 Message-Id: <1434188955-31397-3-git-send-email-mingo@kernel.org> In-Reply-To: <1434188955-31397-1-git-send-email-mingo@kernel.org> References: <1434188955-31397-1-git-send-email-mingo@kernel.org> Sender: owner-linux-mm@kvack.org List-ID: To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, Andy Lutomirski , Andrew Morton , Denys Vlasenko , Brian Gerst , Peter Zijlstra , Borislav Petkov , "H. Peter Anvin" , Linus Torvalds , Oleg Nesterov , Thomas Gleixner , Waiman Long 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 Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Waiman Long Cc: linux-mm@kvack.org Signed-off-by: Ingo Molnar --- arch/x86/mm/init_64.c | 38 +++++++++++++++++++++++++------------- 1 file changed, 25 insertions(+), 13 deletions(-) diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c index 3fba623e3ba5..527d5d4d020c 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 +169,40 @@ 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) { + spin_lock(&pgd_lock); /* Implies rcu_read_lock() for the task list iteration: */ + + for_each_process_thread(g, p) { + struct mm_struct *mm; pgd_t *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; + task_lock(p); + mm = p->mm; + if (!mm) { + task_unlock(p); + continue; + } + + pgd = mm->pgd; + + /* The pgt_lock is only used by Xen: */ + pgt_lock = &mm->page_table_lock; spin_lock(pgt_lock); if (!pgd_none(*pgd_ref) && !pgd_none(*pgd)) - BUG_ON(pgd_page_vaddr(*pgd) - != pgd_page_vaddr(*pgd_ref)); + BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref)); if (removed) { if (pgd_none(*pgd_ref) && !pgd_none(*pgd)) @@ -202,6 +213,7 @@ void sync_global_pgds(unsigned long start, unsigned long end, int removed) } spin_unlock(pgt_lock); + task_unlock(p); } spin_unlock(&pgd_lock); } -- 2.1.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org