From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753225AbcL2QPE (ORCPT ); Thu, 29 Dec 2016 11:15:04 -0500 Received: from mx1.redhat.com ([209.132.183.28]:33402 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753183AbcL2QOo (ORCPT ); Thu, 29 Dec 2016 11:14:44 -0500 From: Waiman Long To: Thomas Gleixner , Ingo Molnar , Peter Zijlstra , Jonathan Corbet Cc: linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, Arnaldo Carvalho de Melo , Davidlohr Bueso , Mike Galbraith , Scott J Norton , Waiman Long Subject: [PATCH v4 20/20] futex: Dump internal futex state via debugfs Date: Thu, 29 Dec 2016 11:13:46 -0500 Message-Id: <1483028026-10305-21-git-send-email-longman@redhat.com> In-Reply-To: <1483028026-10305-1-git-send-email-longman@redhat.com> References: <1483028026-10305-1-git-send-email-longman@redhat.com> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Thu, 29 Dec 2016 16:14:44 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org For debugging purpose, it is sometimes useful to dump the internal states in the futex hash bucket table. This patch adds a file "futex_hash_table" in debugfs root filesystem to dump the internal futex states. Signed-off-by: Waiman Long --- kernel/futex.c | 82 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 82 insertions(+) diff --git a/kernel/futex.c b/kernel/futex.c index 4f235e8..9f7bfd3 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -4425,3 +4425,85 @@ static int __init futex_init(void) return 0; } __initcall(futex_init); + +#if defined(CONFIG_DEBUG_FS) && defined(CONFIG_SMP) +/* + * Debug code to dump selected content of in-kernel futex hash bucket table. + */ +#include + +static int futex_dump_show(struct seq_file *m, void *arg) +{ + struct futex_hash_bucket *hb = arg; + struct futex_state *state; + int i; + + if (list_empty(&hb->fs_head)) + return 0; + + seq_printf(m, "\nHash bucket %ld:\n", hb - futex_queues); + spin_lock(&hb->fs_lock); + i = 0; + list_for_each_entry(state, &hb->fs_head, fs_list) { + seq_printf(m, " Futex state %d\n", i++); + if (state->owner) + seq_printf(m, " owner PID = %d\n", + task_pid_vnr(state->owner)); + if (state->mutex_owner) + seq_printf(m, " mutex owner PID = %d\n", + task_pid_vnr(state->mutex_owner)); + seq_printf(m, " reference count = %d\n", + atomic_read(&state->refcount)); + seq_printf(m, " handoff PID = %d\n", state->handoff_pid); + } + spin_unlock(&hb->fs_lock); + return 0; +} + +static void *futex_dump_start(struct seq_file *m, loff_t *pos) +{ + return (*pos < futex_hashsize) ? &futex_queues[*pos] : NULL; +} + +static void *futex_dump_next(struct seq_file *m, void *arg, loff_t *pos) +{ + (*pos)++; + return (*pos < futex_hashsize) ? &futex_queues[*pos] : NULL; +} + +static void futex_dump_stop(struct seq_file *m, void *arg) +{ +} + +static const struct seq_operations futex_dump_op = { + .start = futex_dump_start, + .next = futex_dump_next, + .stop = futex_dump_stop, + .show = futex_dump_show, +}; + +static int futex_dump_open(struct inode *inode, struct file *file) +{ + return seq_open(file, &futex_dump_op); +} + +static const struct file_operations fops_futex_dump = { + .open = futex_dump_open, + .read = seq_read, + .llseek = seq_lseek, + .release = seq_release, +}; + +/* + * Initialize debugfs for the futex hash bucket table dump. + */ +static int __init init_futex_dump(void) +{ + if (!debugfs_create_file("futex_hash_table", 0400, NULL, NULL, + &fops_futex_dump)) + return -ENOMEM; + return 0; +} +fs_initcall(init_futex_dump); + +#endif /* CONFIG_DEBUG_FS && CONFIG_SMP */ -- 1.8.3.1