git: af928fded070 - main - Add thread_run_flash() helper

[Konstantin Belousov]

The branch main has been updated by kib:

URL: https://cgit.FreeBSD.org/src/commit/?id=af928fded0705100e4f3926c99ed488f7ab6dcf1

commit af928fded0705100e4f3926c99ed488f7ab6dcf1
Author:     Konstantin Belousov <kib at FreeBSD.org>
AuthorDate: 2021-04-24 11:47:53 +0000
Commit:     Konstantin Belousov <kib at FreeBSD.org>
CommitDate: 2021-05-03 16:13:47 +0000

    Add thread_run_flash() helper
    
    It unsuspends single suspended thread, passed as the argument.
    It is up to the caller to arrange the target thread to suspend later,
    since the state of the process is not changed from stopped.  In particular,
    the unsuspended thread must not leave to userspace, since boundary code
    is not prepared to this situation.
    
    Reviewed by:    markj
    Tested by:      pho
    Sponsored by:   The FreeBSD Foundation
    MFC after:      1 week
    Differential revision:  https://reviews.freebsd.org/D29955
---
 sys/kern/kern_thread.c | 25 +++++++++++++++++++++++++
 sys/sys/proc.h         |  1 +
 2 files changed, 26 insertions(+)

diff --git a/sys/kern/kern_thread.c b/sys/kern/kern_thread.c
index ea569576e7c9..d5549baa6ad5 100644
--- a/sys/kern/kern_thread.c
+++ b/sys/kern/kern_thread.c
@@ -1514,6 +1514,31 @@ thread_unsuspend_one(struct thread *td, struct proc *p, bool boundary)
 	return (setrunnable(td, 0));
 }
 
+void
+thread_run_flash(struct thread *td)
+{
+	struct proc *p;
+
+	p = td->td_proc;
+	PROC_LOCK_ASSERT(p, MA_OWNED);
+
+	if (TD_ON_SLEEPQ(td))
+		sleepq_remove_nested(td);
+	else
+		thread_lock(td);
+
+	THREAD_LOCK_ASSERT(td, MA_OWNED);
+	KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended"));
+
+	TD_CLR_SUSPENDED(td);
+	PROC_SLOCK(p);
+	MPASS(p->p_suspcount > 0);
+	p->p_suspcount--;
+	PROC_SUNLOCK(p);
+	if (setrunnable(td, 0))
+		kick_proc0();
+}
+
 /*
  * Allow all threads blocked by single threading to continue running.
  */
diff --git a/sys/sys/proc.h b/sys/sys/proc.h
index b82de183aa44..a078b859ddc1 100644
--- a/sys/sys/proc.h
+++ b/sys/sys/proc.h
@@ -1191,6 +1191,7 @@ void	thread_stopped(struct proc *p);
 void	childproc_stopped(struct proc *child, int reason);
 void	childproc_continued(struct proc *child);
 void	childproc_exited(struct proc *child);
+void	thread_run_flash(struct thread *td);
 int	thread_suspend_check(int how);
 bool	thread_suspend_check_needed(void);
 void	thread_suspend_switch(struct thread *, struct proc *p);