From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754288Ab3A2TGB (ORCPT ); Tue, 29 Jan 2013 14:06:01 -0500 Received: from mailhub.sw.ru ([195.214.232.25]:37090 "EHLO relay.sw.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750913Ab3A2TF5 (ORCPT ); Tue, 29 Jan 2013 14:05:57 -0500 From: Andrey Vagin To: linux-kernel@vger.kernel.org Cc: criu@openvz.org, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org, Andrey Vagin , Oleg Nesterov , Alexander Viro , "Paul E. McKenney" , David Howells , Dave Jones , Michael Kerrisk , Pavel Emelyanov , Cyrill Gorcunov Subject: [PATCH 3/3] signalfd: add ability to read siginfo-s without dequeuing signals (v2) Date: Tue, 29 Jan 2013 23:03:01 +0400 Message-Id: <1359486181-29088-1-git-send-email-avagin@openvz.org> X-Mailer: git-send-email 1.7.11.7 In-Reply-To: <1358849741-9611-4-git-send-email-avagin@openvz.org> References: <1358849741-9611-4-git-send-email-avagin@openvz.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If signalfd is created with the flag SFD_PEEK, it reads siginfo-s without dequeuing signals. For reading not first siginfo pread(fd, buf, size, pos) can be used, where ppos / sizeof(signalfd_siginfo) is a sequence number of a signal in a queue. This functionality is required for checkpointing pending signals. v2: * signals can be dumped only from one queue. * treat pos as offset in bytes, not in elements, so pos should be aligned to the size of signalfd_siginfo. Cc: Oleg Nesterov Cc: Alexander Viro Cc: "Paul E. McKenney" Cc: David Howells Cc: Dave Jones Cc: Andrey Vagin Cc: Michael Kerrisk Cc: Pavel Emelyanov CC: Cyrill Gorcunov Signed-off-by: Andrey Vagin --- fs/signalfd.c | 61 ++++++++++++++++++++++++++++++++++++++++--- include/uapi/linux/signalfd.h | 2 ++ 2 files changed, 60 insertions(+), 3 deletions(-) diff --git a/fs/signalfd.c b/fs/signalfd.c index 8019ec9..0da6a30 100644 --- a/fs/signalfd.c +++ b/fs/signalfd.c @@ -51,6 +51,47 @@ struct signalfd_ctx { sigset_t sigmask; }; +static int peek_signal(struct sigpending *pending, sigset_t *mask, + siginfo_t *info, loff_t *pseq) +{ + struct sigqueue *q; + int ret = 0; + + spin_lock_irq(¤t->sighand->siglock); + + list_for_each_entry(q, &pending->list, list) { + if (sigismember(mask, q->info.si_signo)) + continue; + + if ((*pseq)-- == 0) { + copy_siginfo(info, &q->info); + ret = info->si_signo; + break; + } + } + + spin_unlock_irq(¤t->sighand->siglock); + + return ret; +} + +static ssize_t signalfd_peek(struct signalfd_ctx *ctx, + siginfo_t *info, loff_t *ppos, int queue_mask) +{ + loff_t seq = *ppos / sizeof(struct signalfd_siginfo); + int signr = 0; + + if (queue_mask & SIGQUEUE_PRIVATE) + signr = peek_signal(¤t->pending, + &ctx->sigmask, info, &seq); + else if (queue_mask & SIGQUEUE_SHARED) + signr = peek_signal(¤t->signal->shared_pending, + &ctx->sigmask, info, &seq); + (*ppos) += sizeof(struct signalfd_siginfo); + + return signr; +} + static int signalfd_release(struct inode *inode, struct file *file) { kfree(file->private_data); @@ -257,9 +298,15 @@ static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count, if (!count) return -EINVAL; + if (*ppos % sizeof(struct signalfd_siginfo)) + return -EINVAL; + siginfo = (struct signalfd_siginfo __user *) buf; do { - ret = signalfd_dequeue(ctx, &info, nonblock, qmask); + if (file->f_flags & SFD_PEEK) + ret = signalfd_peek(ctx, &info, ppos, qmask); + else + ret = signalfd_dequeue(ctx, &info, nonblock, qmask); if (unlikely(ret <= 0)) break; @@ -315,7 +362,12 @@ SYSCALL_DEFINE4(signalfd4, int, ufd, sigset_t __user *, user_mask, BUILD_BUG_ON(SFD_CLOEXEC != O_CLOEXEC); BUILD_BUG_ON(SFD_NONBLOCK != O_NONBLOCK); - if (flags & ~(SFD_CLOEXEC | SFD_NONBLOCK | SFD_RAW | SFD_QUEUES)) + if (flags & ~(SFD_CLOEXEC | SFD_NONBLOCK | + SFD_RAW | SFD_PEEK | SFD_QUEUES)) + return -EINVAL; + + /* SFD_PEEK can be used for one queue only */ + if ((flags & SFD_PEEK) && ((flags & SFD_QUEUES) == SFD_QUEUES)) return -EINVAL; if (sizemask != sizeof(sigset_t) || @@ -352,7 +404,10 @@ SYSCALL_DEFINE4(signalfd4, int, ufd, sigset_t __user *, user_mask, } file->f_flags |= (flags & SFD_QUEUES) ? : SFD_QUEUES; - file->f_flags |= flags & SFD_RAW; + file->f_flags |= flags & (SFD_RAW | SFD_PEEK); + + if (file->f_flags & SFD_PEEK) + file->f_mode |= FMODE_PREAD; fd_install(ufd, file); } else { diff --git a/include/uapi/linux/signalfd.h b/include/uapi/linux/signalfd.h index 481b658..24c5d2d 100644 --- a/include/uapi/linux/signalfd.h +++ b/include/uapi/linux/signalfd.h @@ -20,6 +20,8 @@ #define SFD_SHARED_QUEUE O_DIRECTORY /* Read signals from a per-thread queue */ #define SFD_PER_THREAD_QUEUE O_EXCL +/* Read signals without removing them from a queue */ +#define SFD_PEEK O_APPEND struct signalfd_siginfo { __u32 ssi_signo; -- 1.7.11.7