* Anjali Kulkarni <anjali.k.kulka...@oracle.com> [241015 13:30]:
> Add a new type PROC_CN_MCAST_NOTIFY to proc connector API, which allows a
> thread to notify the kernel that is going to exit with a non-zero exit
> code and specify the exit code in it. When thread exits in the kernel,
> it will send this exit code as a proc filter notification to any
> listening process.
> Exiting thread can call this either when it wants to call pthread_exit()
> with non-zero value or from signal handler.
> 
> Add a new file cn_hash.c which implements a hash table storing the exit
> codes of abnormally exiting threads, received by the system call above.
> The key used for the hash table is the pid of the thread, so when the
> thread actually exits, we lookup it's pid in the hash table and retrieve
> the exit code sent by user. If the exit code in struct task is 0, we
> then replace it with the user supplied non-zero exit code.
> 
> cn_hash.c implements the hash table add, delete, lookup operations.
> mutex_lock() and mutex_unlock() operations are used to safeguard the
> integrity of the hash table while adding or deleting elements.
> connector.c has the API calls, called from cn_proc.c, as well as calls
> to allocate, initialize and free the hash table.
> 
> Add a new flag in PF_* flags of task_struct - EXIT_NOTIFY. This flag is
> set when user sends the exit code via PROC_CN_MCAST_NOTIFY. While
> exiting, this flag is checked and the hash table add or delete calls
> are only made if this flag is set.
> 
> A refcount field hrefcnt is added in struct cn_hash_dev, to keep track
> of number of threads which have added an entry in hash table. Before
> freeing the struct cn_hash_dev, this value must be 0.
> 
> Signed-off-by: Anjali Kulkarni <anjali.k.kulka...@oracle.com>
> ---
>  drivers/connector/Makefile    |   2 +-
>  drivers/connector/cn_hash.c   | 195 ++++++++++++++++++++++++++++++++++
>  drivers/connector/cn_proc.c   |  55 +++++++++-
>  drivers/connector/connector.c |  83 ++++++++++++++-
>  include/linux/connector.h     |  43 ++++++++
>  include/linux/sched.h         |   2 +-
>  include/uapi/linux/cn_proc.h  |   4 +-
>  7 files changed, 375 insertions(+), 9 deletions(-)
>  create mode 100644 drivers/connector/cn_hash.c
> 
> diff --git a/drivers/connector/Makefile b/drivers/connector/Makefile
> index 1bf67d3df97d..cb1dcdf067ad 100644
> --- a/drivers/connector/Makefile
> +++ b/drivers/connector/Makefile
> @@ -2,4 +2,4 @@
>  obj-$(CONFIG_CONNECTOR)              += cn.o
>  obj-$(CONFIG_PROC_EVENTS)    += cn_proc.o
>  
> -cn-y                         += cn_queue.o connector.o
> +cn-y                         += cn_hash.o cn_queue.o connector.o
> diff --git a/drivers/connector/cn_hash.c b/drivers/connector/cn_hash.c
> new file mode 100644
> index 000000000000..a0211cd99132
> --- /dev/null
> +++ b/drivers/connector/cn_hash.c
> @@ -0,0 +1,195 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Author: Anjali Kulkarni <anjali.k.kulka...@oracle.com>
> + *
> + * Copyright (c) 2024 Oracle and/or its affiliates.
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/init.h>
> +#include <linux/connector.h>
> +#include <linux/mutex.h>
> +#include <linux/pid_namespace.h>
> +
> +#include <linux/cn_proc.h>
> +
> +struct cn_hash_dev *cn_hash_alloc_dev(const char *name)
> +{
> +     struct cn_hash_dev *hdev;
> +
> +     hdev = kzalloc(sizeof(*hdev), GFP_KERNEL);
> +     if (!hdev)
> +             return NULL;
> +
> +     snprintf(hdev->name, sizeof(hdev->name), "%s", name);
> +     atomic_set(&hdev->hrefcnt, 0);
> +     mutex_init(&hdev->uexit_hash_lock);
> +     hash_init(hdev->uexit_pid_htable);
> +     return hdev;
> +}
> +
> +void cn_hash_free_dev(struct cn_hash_dev *hdev)
> +{
> +     struct uexit_pid_hnode *hnode;
> +     struct hlist_node *tmp;
> +     int bucket;
> +
> +     pr_debug("%s: Freeing entire hdev %p\n", __func__, hdev);
> +
> +     mutex_lock(&hdev->uexit_hash_lock);
> +     hash_for_each_safe(hdev->uexit_pid_htable, bucket, tmp,
> +                     hnode, uexit_pid_hlist) {
> +             hash_del(&hnode->uexit_pid_hlist);
> +             pr_debug("%s: Freeing node for pid %d\n",
> +                             __func__, hnode->pid);
> +             kfree(hnode);
> +     }
> +
> +     mutex_unlock(&hdev->uexit_hash_lock);
> +     mutex_destroy(&hdev->uexit_hash_lock);
> +
> +     while (atomic_read(&hdev->hrefcnt)) {
> +             pr_info("Waiting for %s to become free: refcnt=%d\n",
> +                             hdev->name, atomic_read(&hdev->hrefcnt));
> +             msleep(1000);
> +     }
> +
> +     kfree(hdev);

It might be a good idea to set hdev = NULL here, like
cn_queue_free_dev() does on free since hdev is passed into the function.
Although, I cannot find a reason for this or a comment as to why it was
done - so maybe it's not useful.

> +}
> +
> +static struct uexit_pid_hnode *cn_hash_alloc_elem(__u32 uexit_code, pid_t 
> pid)
> +{
> +     struct uexit_pid_hnode *elem;
> +
> +     elem = kzalloc(sizeof(*elem), GFP_KERNEL);
> +     if (!elem)
> +             return NULL;
> +
> +     INIT_HLIST_NODE(&elem->uexit_pid_hlist);
> +     elem->uexit_code = uexit_code;
> +     elem->pid = pid;
> +     return elem;
> +}
> +
> +void cn_hash_free_elem(struct uexit_pid_hnode *elem)
> +{
> +     kfree(elem);
> +}
> +
> +int cn_hash_add_elem(struct cn_hash_dev *hdev, __u32 uexit_code, pid_t pid)
> +{
> +     struct uexit_pid_hnode *elem, *hnode;
> +
> +     elem = cn_hash_alloc_elem(uexit_code, pid);
> +     if (!elem) {
> +             pr_err("%s: cn_hash_alloc_elem() returned NULL pid %d\n",
> +                             __func__, pid);
> +             return -ENOMEM;
> +     }
> +
> +     mutex_lock(&hdev->uexit_hash_lock);
> +     /*
> +      * Check if an entry for the same pid already exists
> +      */
> +     hash_for_each_possible(hdev->uexit_pid_htable,
> +                             hnode, uexit_pid_hlist, pid) {
> +             if (hnode->pid == pid) {
> +                     mutex_unlock(&hdev->uexit_hash_lock);
> +                     cn_hash_free_elem(elem);
> +                     pr_debug("%s: pid %d already exists in hash table\n",
> +                             __func__, pid);
> +                     return -EEXIST;
> +             }
> +     }
> +
> +     hash_add(hdev->uexit_pid_htable, &elem->uexit_pid_hlist, pid);
> +     mutex_unlock(&hdev->uexit_hash_lock);
> +
> +     atomic_inc(&hdev->hrefcnt);
> +
> +     pr_debug("%s: After hash_add of pid %d elem %p hrefcnt %d\n",
> +                     __func__, pid, elem, atomic_read(&hdev->hrefcnt));
> +     return 0;
> +}
> +
> +int cn_hash_del_elem(struct cn_hash_dev *hdev, pid_t pid)
> +{
> +     struct uexit_pid_hnode *hnode;
> +     struct hlist_node *tmp;
> +
> +     mutex_lock(&hdev->uexit_hash_lock);
> +     hash_for_each_possible_safe(hdev->uexit_pid_htable,
> +                             hnode, tmp, uexit_pid_hlist, pid) {
> +             if (hnode && hnode->pid == pid) {
> +                     hash_del(&hnode->uexit_pid_hlist);
> +                     mutex_unlock(&hdev->uexit_hash_lock);
> +                     kfree(hnode);
> +                     atomic_dec(&hdev->hrefcnt);
> +                     pr_debug("%s: After hash_del of pid %d, hrefcnt %d\n",
> +                                     __func__, pid,
> +                                     atomic_read(&hdev->hrefcnt));
> +                     return 0;
> +             }
> +     }
> +
> +     mutex_unlock(&hdev->uexit_hash_lock);
> +     pr_err("%s: pid %d not found in hash table\n",
> +                     __func__, pid);
> +     return -EINVAL;
> +}
> +
> +__u32 cn_hash_del_get_exval(struct cn_hash_dev *hdev, pid_t pid)
> +{
> +     struct uexit_pid_hnode *hnode;
> +     struct hlist_node *tmp;
> +     __u32 excde;
> +
> +     mutex_lock(&hdev->uexit_hash_lock);
> +     hash_for_each_possible_safe(hdev->uexit_pid_htable,
> +                             hnode, tmp, uexit_pid_hlist, pid) {
> +             if (hnode->pid == pid) {
> +                     excde = hnode->uexit_code;
> +                     hash_del(&hnode->uexit_pid_hlist);
> +                     mutex_unlock(&hdev->uexit_hash_lock);
> +                     kfree(hnode);
> +                     atomic_dec(&hdev->hrefcnt);
> +                     pr_debug("%s: After hash_del of pid %d, found exit code 
> %u hrefcnt %d\n",
> +                                     __func__, pid, excde,
> +                                     atomic_read(&hdev->hrefcnt));
> +                     return excde;
> +             }
> +     }
> +
> +     mutex_unlock(&hdev->uexit_hash_lock);
> +     pr_err("%s: pid %d not found in hash table\n",
> +                     __func__, pid);
> +     return 0;
> +}
> +
> +__u32 cn_hash_get_exval(struct cn_hash_dev *hdev, pid_t pid)
> +{
> +     struct uexit_pid_hnode *hnode;
> +     __u32 excde;
> +
> +     mutex_lock(&hdev->uexit_hash_lock);
> +     hash_for_each_possible(hdev->uexit_pid_htable,
> +                             hnode, uexit_pid_hlist, pid) {
> +             if (hnode->pid == pid) {
> +                     excde = hnode->uexit_code;
> +                     mutex_unlock(&hdev->uexit_hash_lock);
> +                     pr_debug("%s: Found exit code %u for pid %d\n",
> +                                     __func__, excde, pid);
> +                     return excde;
> +             }
> +     }
> +
> +     mutex_unlock(&hdev->uexit_hash_lock);
> +     pr_debug("%s: pid %d not found in hash table\n",
> +                     __func__, pid);
> +     return -EINVAL;
> +}
> +
> +bool cn_hash_table_empty(struct cn_hash_dev *hdev)
> +{
> +     return hash_empty(hdev->uexit_pid_htable);
> +}
> diff --git a/drivers/connector/cn_proc.c b/drivers/connector/cn_proc.c
> index 44b19e696176..9205498fcf0f 100644
> --- a/drivers/connector/cn_proc.c
> +++ b/drivers/connector/cn_proc.c
> @@ -69,6 +69,8 @@ static int cn_filter(struct sock *dsk, struct sk_buff *skb, 
> void *data)
>       if ((__u32)val == PROC_EVENT_ALL)
>               return 0;
>  
> +     pr_debug("%s: val %lx, what %x\n", __func__, val, what);
> +
>       /*
>        * Drop packet if we have to report only non-zero exit status
>        * (PROC_EVENT_NONZERO_EXIT) and exit status is 0
> @@ -326,9 +328,15 @@ void proc_exit_connector(struct task_struct *task)
>       struct proc_event *ev;
>       struct task_struct *parent;
>       __u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);
> +     __u32 uexit_code;
>  
> -     if (atomic_read(&proc_event_num_listeners) < 1)
> +     if (atomic_read(&proc_event_num_listeners) < 1) {
> +             if (likely(!(task->flags & PF_EXIT_NOTIFY)))
> +                     return;
> +
> +             cn_del_elem(task->pid);
>               return;
> +     }
>  
>       msg = buffer_to_cn_msg(buffer);
>       ev = (struct proc_event *)msg->data;
> @@ -337,7 +345,25 @@ void proc_exit_connector(struct task_struct *task)
>       ev->what = PROC_EVENT_EXIT;
>       ev->event_data.exit.process_pid = task->pid;
>       ev->event_data.exit.process_tgid = task->tgid;
> -     ev->event_data.exit.exit_code = task->exit_code;
> +     if (unlikely(task->flags & PF_EXIT_NOTIFY)) {
> +             task->flags &= ~PF_EXIT_NOTIFY;
> +

nit: extra blank line

> +             uexit_code = cn_del_get_exval(task->pid);
> +             if (uexit_code == 0) {
> +                     pr_debug("%s: Returning with task's exit code %u\n",
> +                                     __func__, task->exit_code);
> +                     ev->event_data.exit.exit_code = task->exit_code;
> +             } else {
> +                     ev->event_data.exit.exit_code = uexit_code;
> +                     pr_debug("%s: Reset PF_EXIT_NOTIFY & retrieved exit 
> code %u from hash table, pid %d\n",
> +                                     __func__,
> +                                     ev->event_data.exit.exit_code,
> +                                     task->pid);
> +             }
> +     } else {
> +             ev->event_data.exit.exit_code = task->exit_code;
> +     }
> +
>       ev->event_data.exit.exit_signal = task->exit_signal;
>  
>       rcu_read_lock();
> @@ -413,6 +439,13 @@ static void cn_proc_mcast_ctl(struct cn_msg *msg,
>       if (msg->len == sizeof(*pinput)) {
>               pinput = (struct proc_input *)msg->data;
>               mc_op = pinput->mcast_op;
> +             if (mc_op == PROC_CN_MCAST_NOTIFY) {
> +                     pr_debug("%s: Received PROC_CN_MCAST_NOTIFY, pid %d\n",
> +                                     __func__, current->pid);
> +                     current->flags |= PF_EXIT_NOTIFY;
> +                     err = cn_add_elem(pinput->uexit_code, current->pid);
> +                     return;
> +             }
>               ev_type = pinput->event_type;
>       } else if (msg->len == sizeof(mc_op)) {
>               mc_op = *((enum proc_cn_mcast_op *)msg->data);
> @@ -432,6 +465,8 @@ static void cn_proc_mcast_ctl(struct cn_msg *msg,
>                       sk->sk_user_data = kzalloc(sizeof(struct proc_input),
>                                                  GFP_KERNEL);
>                       if (sk->sk_user_data == NULL) {
> +                             pr_err("%s: ENOMEM for sk_user_data, pid %d\n",
> +                                             __func__, current->pid);
>                               err = ENOMEM;
>                               goto out;
>                       }
> @@ -442,21 +477,33 @@ static void cn_proc_mcast_ctl(struct cn_msg *msg,
>               }
>               ((struct proc_input *)(sk->sk_user_data))->event_type =
>                       ev_type;
> +             pr_debug("%s: sk: %p pid: %d event_type: %x\n",
> +                             __func__, sk, current->pid, ev_type);
>               ((struct proc_input *)(sk->sk_user_data))->mcast_op = mc_op;
>       }
>  
>       switch (mc_op) {
>       case PROC_CN_MCAST_LISTEN:
> -             if (initial || (prev_mc_op != PROC_CN_MCAST_LISTEN))
> +             if (initial || (prev_mc_op != PROC_CN_MCAST_LISTEN)) {
>                       atomic_inc(&proc_event_num_listeners);
> +                     pr_debug("%s: PROC_CN_MCAST_LISTEN pid %d: Incremented 
> listeners to %d\n",
> +                                     __func__, current->pid,
> +                                     atomic_read(&proc_event_num_listeners));
> +             }
>               break;
>       case PROC_CN_MCAST_IGNORE:
> -             if (!initial && (prev_mc_op != PROC_CN_MCAST_IGNORE))
> +             if (!initial && (prev_mc_op != PROC_CN_MCAST_IGNORE)) {
>                       atomic_dec(&proc_event_num_listeners);
> +                     pr_debug("%s: PROC_CN_MCAST_IGNORE pid %d: Decremented 
> listeners to %d\n",
> +                                     __func__, current->pid,
> +                                     atomic_read(&proc_event_num_listeners));
> +             }
>               ((struct proc_input *)(sk->sk_user_data))->event_type =
>                       PROC_EVENT_NONE;
>               break;
>       default:
> +             pr_warn("%s: Invalid value for mc_op %d\n",
> +                             __func__, mc_op);

nit: Does this need to be split to two lines?

>               err = EINVAL;
>               break;
>       }
> diff --git a/drivers/connector/connector.c b/drivers/connector/connector.c
> index 4028e8eeba82..506e3cbedf85 100644
> --- a/drivers/connector/connector.c
> +++ b/drivers/connector/connector.c
> @@ -271,6 +271,67 @@ static int __maybe_unused cn_proc_show(struct seq_file 
> *m, void *v)
>       return 0;
>  }
>  
> +__u32 cn_del_get_exval(pid_t pid)
> +{
> +     struct cn_dev *dev = &cdev;
> +     __u32 exval;
> +
> +     if (!cn_already_initialized)
> +             return 0;
> +
> +     exval = cn_hash_del_get_exval(dev->hdev, pid);
> +     return exval;

You can remove exval from this function by returning the result directly.

> +}
> +EXPORT_SYMBOL_GPL(cn_del_get_exval);
> +
> +int cn_del_elem(pid_t pid)
> +{
> +     struct cn_dev *dev = &cdev;
> +     int ret;
> +
> +     if (!cn_already_initialized)
> +             return 0;
> +
> +     ret = cn_hash_del_elem(dev->hdev, pid);
> +     return ret;

You can remove ret from this function by returning the result directly.

> +}
> +EXPORT_SYMBOL_GPL(cn_del_elem);
> +
> +int cn_add_elem(__u32 uexit_code, pid_t pid)
> +{
> +     struct cn_dev *dev = &cdev;
> +
> +     if (!cn_already_initialized)
> +             return 0;
> +
> +     return cn_hash_add_elem(dev->hdev, uexit_code, pid);
> +}
> +EXPORT_SYMBOL_GPL(cn_add_elem);
> +
> +__u32 cn_get_exval(pid_t pid)
> +{
> +     struct cn_dev *dev = &cdev;
> +     __u32 exval;
> +
> +     if (!cn_already_initialized)
> +             return 0;
> +
> +     exval = cn_hash_get_exval(dev->hdev, pid);
> +     return exval;

You can remove exval from this function by returning the result directly.

> +}
> +EXPORT_SYMBOL_GPL(cn_get_exval);
> +
> +bool cn_table_empty(void)
> +{
> +     struct cn_dev *dev = &cdev;
> +
> +     if (!cn_already_initialized)
> +             return 0;
> +
> +     return cn_hash_table_empty(dev->hdev);
> +}
> +EXPORT_SYMBOL_GPL(cn_table_empty);
> +
>  static int cn_init(void)
>  {
>       struct cn_dev *dev = &cdev;
> @@ -283,18 +344,35 @@ static int cn_init(void)
>       };
>  
>       dev->nls = netlink_kernel_create(&init_net, NETLINK_CONNECTOR, &cfg);
> -     if (!dev->nls)
> +     if (!dev->nls) {
> +             pr_err("%s: netlink_kernel_create failed, connector not 
> initialized\n",
> +                             __func__);
>               return -EIO;
> +     }
>  
>       dev->cbdev = cn_queue_alloc_dev("cqueue", dev->nls);
>       if (!dev->cbdev) {
> +             pr_err("%s: Allocation of dev->cbdev failed, connector not 
> initialized\n",
> +                             __func__);
>               netlink_kernel_release(dev->nls);
>               return -EINVAL;
>       }
>  
> +     dev->hdev = cn_hash_alloc_dev("pid hash table");
> +     if (!dev->hdev) {
> +             pr_err("%s: Allocation of dev->hdev failed, connector not 
> initialized\n",
> +                             __func__);
> +             netlink_kernel_release(dev->nls);
> +             cn_queue_free_dev(dev->cbdev);
> +             return -ENOMEM;
> +     }
> +
> +     pr_debug("Connector initialized, allocated hdev %p\n", dev->hdev);
> +
>       cn_already_initialized = 1;
>  
> -     proc_create_single("connector", S_IRUGO, init_net.proc_net, 
> cn_proc_show);
> +     proc_create_single("connector", S_IRUGO, init_net.proc_net,
> +                             cn_proc_show);

Unnecessary change here.

>  
>       return 0;
>  }
> @@ -308,6 +386,7 @@ static void cn_fini(void)
>       remove_proc_entry("connector", init_net.proc_net);
>  
>       cn_queue_free_dev(dev->cbdev);
> +     cn_hash_free_dev(dev->hdev);
>       netlink_kernel_release(dev->nls);
>  }
>  
> diff --git a/include/linux/connector.h b/include/linux/connector.h
> index 70bc1160f3d8..094e1730a4f6 100644
> --- a/include/linux/connector.h
> +++ b/include/linux/connector.h
> @@ -18,6 +18,8 @@
>  #include <uapi/linux/connector.h>
>  
>  #define CN_CBQ_NAMELEN               32
> +#define HASHT_NAMELEN                32
> +#define PID_HASH_TABLE_BITS  10
>  
>  struct cn_queue_dev {
>       atomic_t refcnt;
> @@ -45,6 +47,19 @@ struct cn_callback_entry {
>       u32 seq, group;
>  };
>  
> +struct uexit_pid_hnode {
> +     __u32 uexit_code;
> +     pid_t pid;
> +     struct hlist_node uexit_pid_hlist;
> +};
> +
> +struct cn_hash_dev {
> +     atomic_t hrefcnt;
> +     unsigned char name[HASHT_NAMELEN];
> +     struct mutex uexit_hash_lock;
> +     DECLARE_HASHTABLE(uexit_pid_htable, PID_HASH_TABLE_BITS);
> +};
> +
>  struct cn_dev {
>       struct cb_id id;
>  
> @@ -52,6 +67,7 @@ struct cn_dev {
>       struct sock *nls;
>  
>       struct cn_queue_dev *cbdev;
> +     struct cn_hash_dev *hdev;
>  };
>  
>  /**
> @@ -137,4 +153,31 @@ void cn_queue_free_dev(struct cn_queue_dev *dev);
>  
>  int cn_cb_equal(const struct cb_id *, const struct cb_id *);
>  
> +struct cn_hash_dev *cn_hash_alloc_dev(const char *name);
> +void cn_hash_free_dev(struct cn_hash_dev *hdev);
> +struct uexit_pid_hnode *cn_hash_find_pid_node(struct cn_hash_dev *hdev,
> +                                             pid_t pid);
> +void cn_hash_free_elem(struct uexit_pid_hnode *elem);
> +int cn_hash_add_elem(struct cn_hash_dev *hdev, __u32 uexit_code, pid_t pid);
> +int cn_hash_del_elem(struct cn_hash_dev *hdev, pid_t pid);
> +__u32 cn_hash_del_get_exval(struct cn_hash_dev *hdev, pid_t pid);
> +
> +int cn_add_elem(__u32 uexit_code, pid_t pid);
> +int cn_del_elem(pid_t pid);
> +__u32 cn_del_get_exval(pid_t pid);
> +__u32 cn_get_exval(pid_t pid);
> +
> +struct cn_hash_dev *cn_hash_alloc_dev(const char *name);
> +void cn_hash_free_dev(struct cn_hash_dev *hdev);
> +struct uexit_pid_hnode *cn_hash_find_pid_node(struct cn_hash_dev *hdev,
> +                                             pid_t pid);
> +void cn_hash_free_elem(struct uexit_pid_hnode *elem);
> +int cn_hash_add_elem(struct cn_hash_dev *hdev, __u32 uexit_code, pid_t pid);
> +int cn_hash_del_elem(struct cn_hash_dev *hdev, pid_t pid);
> +__u32 cn_hash_del_get_exval(struct cn_hash_dev *hdev, pid_t pid);
> +__u32 cn_hash_get_exval(struct cn_hash_dev *hdev, pid_t pid);
> +

Why are these here twice?  Am I missing something?

It also seems like a lot of these can be static inline and removed
completely from the header as they are not used externally.

> +bool cn_table_empty(void);
> +bool cn_hash_table_empty(struct cn_hash_dev *hdev);
> +
>  #endif                               /* __CONNECTOR_H */
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index e6ee4258169a..a2339ae6208b 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -1673,7 +1673,7 @@ extern struct pid *cad_pid;
>  #define PF_USED_MATH         0x00002000      /* If unset the fpu must be 
> initialized before use */
>  #define PF_USER_WORKER               0x00004000      /* Kernel thread cloned 
> from userspace thread */
>  #define PF_NOFREEZE          0x00008000      /* This thread should not be 
> frozen */
> -#define PF__HOLE__00010000   0x00010000
> +#define PF_EXIT_NOTIFY               0x00010000      /* This thread has sent 
> an exit value to be sent as a notification to listening processes */
>  #define PF_KSWAPD            0x00020000      /* I am kswapd */
>  #define PF_MEMALLOC_NOFS     0x00040000      /* All allocations inherit 
> GFP_NOFS. See memalloc_nfs_save() */
>  #define PF_MEMALLOC_NOIO     0x00080000      /* All allocations inherit 
> GFP_NOIO. See memalloc_noio_save() */
> diff --git a/include/uapi/linux/cn_proc.h b/include/uapi/linux/cn_proc.h
> index 18e3745b86cd..2b12a24e4651 100644
> --- a/include/uapi/linux/cn_proc.h
> +++ b/include/uapi/linux/cn_proc.h
> @@ -27,7 +27,8 @@
>   */
>  enum proc_cn_mcast_op {
>       PROC_CN_MCAST_LISTEN = 1,
> -     PROC_CN_MCAST_IGNORE = 2
> +     PROC_CN_MCAST_IGNORE = 2,
> +     PROC_CN_MCAST_NOTIFY = 3
>  };
>  
>  #define PROC_EVENT_ALL (PROC_EVENT_FORK | PROC_EVENT_EXEC | PROC_EVENT_UID | 
>  \
> @@ -65,6 +66,7 @@ enum proc_cn_event {
>  struct proc_input {
>       enum proc_cn_mcast_op mcast_op;
>       enum proc_cn_event event_type;
> +     __u32 uexit_code;
>  };
>  
>  static inline enum proc_cn_event valid_event(enum proc_cn_event ev_type)
> -- 
> 2.46.0
> 

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