[PATCH 8/9] um: Support directing IO signals to calling thread

[Tiwei Bie <tiwei.bie@linux.dev>]

From: Tiwei Bie <tiwei.btw@antgroup.com>

Extend os_set_fd_async() to allow the calling thread to direct
I/O availability signals to itself. After this change, existing
users will explicitly direct these signals to the CPU0 thread,
which was achieved by ignoring SIGIO in helper threads. This is
a preparation for adding SMP support.

Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
---
 arch/um/include/shared/os.h |  2 +-
 arch/um/kernel/irq.c        |  4 ++--
 arch/um/os-Linux/file.c     | 10 +++++++---
 3 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/arch/um/include/shared/os.h b/arch/um/include/shared/os.h
index 0ca6e4548671..ca377421181d 100644
--- a/arch/um/include/shared/os.h
+++ b/arch/um/include/shared/os.h
@@ -155,7 +155,7 @@ extern int os_pread_file(int fd, void *buf, int len, unsigned long long offset);
 extern int os_pwrite_file(int fd, const void *buf, int count, unsigned long long offset);
 extern int os_file_modtime(const char *file, long long *modtime);
 extern int os_pipe(int *fd, int stream, int close_on_exec);
-extern int os_set_fd_async(int fd);
+extern int os_set_fd_async(int fd, int self);
 extern int os_clear_fd_async(int fd);
 extern int os_set_fd_block(int fd, int blocking);
 extern int os_accept_connection(int fd);
diff --git a/arch/um/kernel/irq.c b/arch/um/kernel/irq.c
index 5ed8014e43e4..193b6374d890 100644
--- a/arch/um/kernel/irq.c
+++ b/arch/um/kernel/irq.c
@@ -302,7 +302,7 @@ static int activate_fd(int irq, int fd, enum um_irq_type type, void *dev_id,
 	int err, events = os_event_mask(type);
 	unsigned long flags;
 
-	err = os_set_fd_async(fd);
+	err = os_set_fd_async(fd, 0);
 	if (err < 0)
 		goto out;
 
@@ -607,7 +607,7 @@ void um_irqs_resume(void)
 	raw_spin_lock_irqsave(&irq_lock, flags);
 	list_for_each_entry(entry, &active_fds, list) {
 		if (entry->suspended) {
-			int err = os_set_fd_async(entry->fd);
+			int err = os_set_fd_async(entry->fd, 0);
 
 			WARN(err < 0, "os_set_fd_async returned %d\n", err);
 			entry->suspended = false;
diff --git a/arch/um/os-Linux/file.c b/arch/um/os-Linux/file.c
index 617886d1fb1e..2544a0fc9fbb 100644
--- a/arch/um/os-Linux/file.c
+++ b/arch/um/os-Linux/file.c
@@ -391,8 +391,12 @@ int os_pipe(int *fds, int stream, int close_on_exec)
 	return err;
 }
 
-int os_set_fd_async(int fd)
+int os_set_fd_async(int fd, int self)
 {
+	struct f_owner_ex owner = {
+		.type = F_OWNER_TID,
+		.pid = self ? gettid() : os_getpid(),
+	};
 	int err, flags;
 
 	flags = fcntl(fd, F_GETFL);
@@ -408,9 +412,9 @@ int os_set_fd_async(int fd)
 	}
 
 	if ((fcntl(fd, F_SETSIG, SIGIO) < 0) ||
-	    (fcntl(fd, F_SETOWN, os_getpid()) < 0)) {
+	    (fcntl(fd, F_SETOWN_EX, &owner) < 0)) {
 		err = -errno;
-		printk(UM_KERN_ERR "os_set_fd_async : Failed to fcntl F_SETOWN "
+		printk(UM_KERN_ERR "os_set_fd_async : Failed to fcntl F_SETOWN_EX "
 		       "(or F_SETSIG) fd %d, errno = %d\n", fd, errno);
 		return err;
 	}
-- 
2.34.1