From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f174.google.com (mail-wi0-f174.google.com [209.85.212.174]) by kanga.kvack.org (Postfix) with ESMTP id 38770280324 for ; Fri, 17 Jul 2015 08:22:11 -0400 (EDT) Received: by wibud3 with SMTP id ud3so37991581wib.1 for ; Fri, 17 Jul 2015 05:22:10 -0700 (PDT) Received: from mx2.suse.de (cantor2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id 10si19220090wjr.158.2015.07.17.05.22.08 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Fri, 17 Jul 2015 05:22:09 -0700 (PDT) From: Mel Gorman Subject: [PATCH 1/3] mm, meminit: replace rwsem with completion Date: Fri, 17 Jul 2015 13:22:02 +0100 Message-Id: <1437135724-20110-2-git-send-email-mgorman@suse.de> In-Reply-To: <1437135724-20110-1-git-send-email-mgorman@suse.de> References: <1437135724-20110-1-git-send-email-mgorman@suse.de> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Nicolai Stange , Peter Zijlstra , Dave Hansen , Alex Ng , Fengguang Wu , Linux-MM , LKML , Mel Gorman From: Nicolai Stange Commit 0e1cc95b4cc7 ("mm: meminit: finish initialisation of struct pages before basic setup") introduced a rwsem to signal completion of the initialization workers. Lockdep complains about possible recursive locking: ============================================= [ INFO: possible recursive locking detected ] 4.1.0-12802-g1dc51b8 #3 Not tainted --------------------------------------------- swapper/0/1 is trying to acquire lock: (pgdat_init_rwsem){++++.+}, at: [] page_alloc_init_late+0xc7/0xe6 but task is already holding lock: (pgdat_init_rwsem){++++.+}, at: [] page_alloc_init_late+0x3e/0xe6 Replace the rwsem by a completion together with an atomic "outstanding work counter". [peterz@infradead.org: Barrier removal on the grounds of being pointless] [mgorman@suse.de: Applied review feedback] Signed-off-by: Nicolai Stange Signed-off-by: Mel Gorman --- mm/page_alloc.c | 22 +++++++++++++++------- 1 file changed, 15 insertions(+), 7 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 506eac8b38af..a69e78c396a0 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -18,7 +18,6 @@ #include #include #include -#include #include #include #include @@ -1062,7 +1061,15 @@ static void __init deferred_free_range(struct page *page, __free_pages_boot_core(page, pfn, 0); } -static __initdata DECLARE_RWSEM(pgdat_init_rwsem); +/* Completion tracking for deferred_init_memmap() threads */ +static atomic_t pgdat_init_n_undone __initdata; +static __initdata DECLARE_COMPLETION(pgdat_init_all_done_comp); + +static inline void __init pgdat_init_report_one_done(void) +{ + if (atomic_dec_and_test(&pgdat_init_n_undone)) + complete(&pgdat_init_all_done_comp); +} /* Initialise remaining memory on a node */ static int __init deferred_init_memmap(void *data) @@ -1079,7 +1086,7 @@ static int __init deferred_init_memmap(void *data) const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id); if (first_init_pfn == ULONG_MAX) { - up_read(&pgdat_init_rwsem); + pgdat_init_report_one_done(); return 0; } @@ -1179,7 +1186,8 @@ free_range: pr_info("node %d initialised, %lu pages in %ums\n", nid, nr_pages, jiffies_to_msecs(jiffies - start)); - up_read(&pgdat_init_rwsem); + + pgdat_init_report_one_done(); return 0; } @@ -1187,14 +1195,14 @@ void __init page_alloc_init_late(void) { int nid; + /* There will be num_node_state(N_MEMORY) threads */ + atomic_set(&pgdat_init_n_undone, num_node_state(N_MEMORY)); for_each_node_state(nid, N_MEMORY) { - down_read(&pgdat_init_rwsem); kthread_run(deferred_init_memmap, NODE_DATA(nid), "pgdatinit%d", nid); } /* Block until all are initialised */ - down_write(&pgdat_init_rwsem); - up_write(&pgdat_init_rwsem); + wait_for_completion(&pgdat_init_all_done_comp); } #endif /* CONFIG_DEFERRED_STRUCT_PAGE_INIT */ -- 2.4.3 -- 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