Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755223Ab2KMQVF (ORCPT ); Tue, 13 Nov 2012 11:21:05 -0500 Received: from mail-la0-f46.google.com ([209.85.215.46]:53146 "EHLO mail-la0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752108Ab2KMQVD (ORCPT ); Tue, 13 Nov 2012 11:21:03 -0500 Date: Tue, 13 Nov 2012 20:20:56 +0400 From: Cyrill Gorcunov To: Oleg Nesterov , Pavel Emelyanov Cc: Al Viro , Alexey Dobriyan , James Bottomley , "Aneesh Kumar K.V" , Matthew Helsley , "J. Bruce Fields" , Andrew Morton , linux-kernel@vger.kernel.org Subject: Re: + fs-epoll-add-procfs-fdinfo-helper.patch added to -mm tree Message-ID: <20121113162056.GK7808@moon> References: <20121113145050.GA13691@redhat.com> <20121113155313.GU6511@moon> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20121113155313.GU6511@moon> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4180 Lines: 131 On Tue, Nov 13, 2012 at 07:53:13PM +0400, Cyrill Gorcunov wrote: > On Tue, Nov 13, 2012 at 03:50:50PM +0100, Oleg Nesterov wrote: > > This doesn't look right. > > > > The problem is, the current locking is broken, ->siglock can not serialize > > ->sigmask changes. Just suppose the the child inherits sigfd from parent > > and they both do sys_signalfd4() at the same time. > > > > Nothing really bad can happen, that is why nobody bothers to fix this. > > But this patch makes the thing worse, write_seqcount_begin() must be > > serialized correctly. > > Thanks a lot, Oleg! I'll update. Something like below? --- From: Cyrill Gorcunov Subject: fdinfo: Show sigmask for signalfd fd v3 Signed-off-by: Cyrill Gorcunov CC: Pavel Emelyanov CC: Al Viro CC: Alexey Dobriyan CC: Andrew Morton CC: James Bottomley CC: "Aneesh Kumar K.V" CC: Alexey Dobriyan CC: Matthew Helsley CC: "J. Bruce Fields" CC: "Aneesh Kumar K.V" --- fs/proc/array.c | 2 +- fs/signalfd.c | 24 ++++++++++++++++++++++++ include/linux/proc_fs.h | 3 +++ 3 files changed, 28 insertions(+), 1 deletion(-) Index: linux-2.6.git/fs/proc/array.c =================================================================== --- linux-2.6.git.orig/fs/proc/array.c +++ linux-2.6.git/fs/proc/array.c @@ -220,7 +220,7 @@ static inline void task_state(struct seq seq_putc(m, '\n'); } -static void render_sigset_t(struct seq_file *m, const char *header, +void render_sigset_t(struct seq_file *m, const char *header, sigset_t *set) { int i; Index: linux-2.6.git/fs/signalfd.c =================================================================== --- linux-2.6.git.orig/fs/signalfd.c +++ linux-2.6.git/fs/signalfd.c @@ -29,6 +29,7 @@ #include #include #include +#include void signalfd_cleanup(struct sighand_struct *sighand) { @@ -46,6 +47,7 @@ void signalfd_cleanup(struct sighand_str } struct signalfd_ctx { + rwlock_t lock; sigset_t sigmask; }; @@ -227,7 +229,26 @@ static ssize_t signalfd_read(struct file return total ? total: ret; } +#ifdef CONFIG_PROC_FS +static int signalfd_show_fdinfo(struct seq_file *m, struct file *f) +{ + struct signalfd_ctx *ctx = f->private_data; + sigset_t sigmask; + + read_lock(&ctx->lock); + sigmask = ctx->sigmask; + read_unlock(&ctx->lock); + + signotset(&sigmask); + render_sigset_t(m, "sigmask:\t", &sigmask); + return 0; +} +#endif + static const struct file_operations signalfd_fops = { +#ifdef CONFIG_PROC_FS + .show_fdinfo = signalfd_show_fdinfo, +#endif .release = signalfd_release, .poll = signalfd_poll, .read = signalfd_read, @@ -259,6 +280,7 @@ SYSCALL_DEFINE4(signalfd4, int, ufd, sig return -ENOMEM; ctx->sigmask = sigmask; + rwlock_init(&ctx->lock); /* * When we call this, the initialization must be complete, since @@ -278,7 +300,9 @@ SYSCALL_DEFINE4(signalfd4, int, ufd, sig return -EINVAL; } spin_lock_irq(¤t->sighand->siglock); + write_lock(&ctx->lock); ctx->sigmask = sigmask; + write_unlock(&ctx->lock); spin_unlock_irq(¤t->sighand->siglock); wake_up(¤t->sighand->signalfd_wqh); Index: linux-2.6.git/include/linux/proc_fs.h =================================================================== --- linux-2.6.git.orig/include/linux/proc_fs.h +++ linux-2.6.git/include/linux/proc_fs.h @@ -290,4 +290,7 @@ static inline struct net *PDE_NET(struct return pde->parent->data; } +#include + +void render_sigset_t(struct seq_file *m, const char *header, sigset_t *set); #endif /* _LINUX_PROC_FS_H */ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/