Commit 33c9da5d authored by Tiwei Bie's avatar Tiwei Bie Committed by Johannes Berg
Browse files

um: Rewrite the sigio workaround based on epoll and tgkill 



The existing sigio workaround implementation removes FDs from the
poll when events are triggered, requiring users to re-add them via
add_sigio_fd() after processing. This introduces a potential race
condition between FD removal in write_sigio_thread() and next_poll
update in __add_sigio_fd(), and is inefficient due to frequent FD
removal and re-addition. Rewrite the implementation based on epoll
and tgkill for improved efficiency and reliability.

Signed-off-by: default avatarTiwei Bie <tiwei.btw@antgroup.com>
Link: https://patch.msgid.link/20250315161910.4082396-2-tiwei.btw@antgroup.com


Signed-off-by: default avatarJohannes Berg <johannes.berg@intel.com>
parent 69f52573

arch/um/drivers/random.c

+1 −1
Original line number Diff line number Diff line
@@ -79,7 +79,7 @@ static int __init rng_init (void) 
	if (err < 0)

		goto err_out_cleanup_hw;



	sigio_broken(random_fd);

	sigio_broken();

	hwrng.name = RNG_MODULE_NAME;

	hwrng.read = rng_dev_read;

arch/um/drivers/rtc_user.c

+1 −1
Original line number Diff line number Diff line
@@ -39,7 +39,7 @@ int uml_rtc_start(bool timetravel) 
		}



		/* apparently timerfd won't send SIGIO, use workaround */

		sigio_broken(uml_rtc_irq_fds[0]);

		sigio_broken();

		err = add_sigio_fd(uml_rtc_irq_fds[0]);

		if (err < 0) {

			close(uml_rtc_irq_fds[0]);

arch/um/include/shared/os.h

+1 −1
Original line number Diff line number Diff line
@@ -314,7 +314,7 @@ extern void um_irqs_resume(void); 
extern int add_sigio_fd(int fd);

extern int ignore_sigio_fd(int fd);

extern void maybe_sigio_broken(int fd);

extern void sigio_broken(int fd);

extern void sigio_broken(void);

/*

 * unlocked versions for IRQ controller code.

 *

arch/um/include/shared/sigio.h

+0 −1
Original line number Diff line number Diff line
@@ -6,7 +6,6 @@ 
#ifndef __SIGIO_H__

#define __SIGIO_H__



extern int write_sigio_irq(int fd);

extern void sigio_lock(void);

extern void sigio_unlock(void);

arch/um/kernel/sigio.c

+0 −26
Original line number Diff line number Diff line
@@ -8,32 +8,6 @@ 
#include <os.h>

#include <sigio.h>



/* Protected by sigio_lock() called from write_sigio_workaround */

static int sigio_irq_fd = -1;



static irqreturn_t sigio_interrupt(int irq, void *data)

{

	char c;



	os_read_file(sigio_irq_fd, &c, sizeof(c));

	return IRQ_HANDLED;

}



int write_sigio_irq(int fd)

{

	int err;



	err = um_request_irq(SIGIO_WRITE_IRQ, fd, IRQ_READ, sigio_interrupt,

			     0, "write sigio", NULL);

	if (err < 0) {

		printk(KERN_ERR "write_sigio_irq : um_request_irq failed, "

		       "err = %d\n", err);

		return -1;

	}

	sigio_irq_fd = fd;

	return 0;

}



/* These are called from os-Linux/sigio.c to protect its pollfds arrays. */

static DEFINE_MUTEX(sigio_mutex);