[PATCH 3/4] signalfd: add ability to choose a private or shared queue

[Andrey Vagin]

This patch is added two flags SFD_GROUP and SFD_SHARED.
SFD_SHARED - read signals from a shared queue
SFD_PRIVATE - read signals from a private queue

Without this flags or with both flags signals are read from both queues.

This functionality is requered for dumping pending signals.

Cc: Alexander Viro <v...@zeniv.linux.org.uk>
Cc: "Paul E. McKenney" <paul...@linux.vnet.ibm.com>
Cc: David Howells <dhowe...@redhat.com>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: Oleg Nesterov <o...@redhat.com>
Cc: Michael Kerrisk <mtk.manpa...@gmail.com>
Cc: Pavel Emelyanov <xe...@parallels.com>
CC: Cyrill Gorcunov <gorcu...@openvz.org>
Signed-off-by: Andrey Vagin <ava...@openvz.org>
---
 fs/signalfd.c                 | 25 +++++++++++++++++++------
 include/uapi/linux/signalfd.h |  2 ++
 2 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/fs/signalfd.c b/fs/signalfd.c
index 95f1444..a35aeda 100644
--- a/fs/signalfd.c
+++ b/fs/signalfd.c
@@ -170,13 +170,13 @@ static int signalfd_copyinfo(struct signalfd_siginfo 
__user *uinfo,
 }
 
 static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, siginfo_t *info,
-                               int nonblock)
+                               int nonblock, int queue)
 {
        ssize_t ret;
        DECLARE_WAITQUEUE(wait, current);
 
        spin_lock_irq(&current->sighand->siglock);
-       ret = dequeue_signal(current, &ctx->sigmask, info);
+       ret = do_dequeue_signal(current, &ctx->sigmask, info, queue);
        switch (ret) {
        case 0:
                if (!nonblock)
@@ -223,14 +223,21 @@ static ssize_t signalfd_read(struct file *file, char 
__user *buf, size_t count,
        bool raw = file->f_flags & SFD_RAW;
        ssize_t ret, total = 0;
        siginfo_t info;
+       int queue = 0;
 
        count /= sizeof(struct signalfd_siginfo);
        if (!count)
                return -EINVAL;
 
+       if (file->f_flags & SFD_GROUP)
+               queue++;
+
+       if (file->f_flags & SFD_PRIVATE)
+               queue--;
+
        siginfo = (struct signalfd_siginfo __user *) buf;
        do {
-               ret = signalfd_dequeue(ctx, &info, nonblock);
+               ret = signalfd_dequeue(ctx, &info, nonblock, queue);
                if (unlikely(ret <= 0))
                        break;
 
@@ -274,6 +281,8 @@ static const struct file_operations signalfd_fops = {
        .llseek         = noop_llseek,
 };
 
+#define SIGNAFD_FLAGS (SFD_RAW | SFD_GROUP | SFD_PRIVATE)
+
 SYSCALL_DEFINE4(signalfd4, int, ufd, sigset_t __user *, user_mask,
                size_t, sizemask, int, flags)
 {
@@ -284,7 +293,7 @@ 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))
+       if (flags & ~(SFD_CLOEXEC | SFD_NONBLOCK | SIGNAFD_FLAGS))
                return -EINVAL;
 
        if (sizemask != sizeof(sigset_t) ||
@@ -308,9 +317,9 @@ SYSCALL_DEFINE4(signalfd4, int, ufd, sigset_t __user *, 
user_mask,
                                       O_RDWR | (flags & (O_CLOEXEC | 
O_NONBLOCK)));
                if (ufd < 0)
                        kfree(ctx);
-               else if (flags & SFD_RAW) {
+               else if (flags & SIGNAFD_FLAGS) {
                        struct fd f = fdget(ufd);
-                       f.file->f_flags |= flags & SFD_RAW;
+                       f.file->f_flags |= flags & SIGNAFD_FLAGS;
                        fdput(f);
                }
        } else {
@@ -322,6 +331,10 @@ SYSCALL_DEFINE4(signalfd4, int, ufd, sigset_t __user *, 
user_mask,
                        fdput(f);
                        return -EINVAL;
                }
+
+               f.file->f_flags = (f.file->f_flags & ~SIGNAFD_FLAGS) |
+                                               (flags & SIGNAFD_FLAGS);
+
                spin_lock_irq(&current->sighand->siglock);
                ctx->sigmask = sigmask;
                spin_unlock_irq(&current->sighand->siglock);
diff --git a/include/uapi/linux/signalfd.h b/include/uapi/linux/signalfd.h
index bc31849..9421321 100644
--- a/include/uapi/linux/signalfd.h
+++ b/include/uapi/linux/signalfd.h
@@ -16,6 +16,8 @@
 #define SFD_CLOEXEC O_CLOEXEC
 #define SFD_NONBLOCK O_NONBLOCK
 #define SFD_RAW O_DIRECT
+#define SFD_GROUP O_DIRECTORY
+#define SFD_PRIVATE O_EXCL
 
 struct signalfd_siginfo {
        __u32 ssi_signo;
-- 
1.7.11.7

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