git: 06dae2185fc2 - stable/15 - proc: add tree ref count

The branch stable/15 has been updated by kib:

URL: https://cgit.FreeBSD.org/src/commit/?id=06dae2185fc249ef30f13c343cc7139f20739671

commit 06dae2185fc249ef30f13c343cc7139f20739671
Author:     Konstantin Belousov <kib@FreeBSD.org>
AuthorDate: 2026-06-06 18:02:29 +0000
Commit:     Konstantin Belousov <kib@FreeBSD.org>
CommitDate: 2026-06-13 00:58:37 +0000

    proc: add tree ref count
    
    (cherry picked from commit 85a65e3930924429903e09832d177f8aa09dfb47)
---
 sys/kern/kern_exit.c | 2 +-
 sys/kern/kern_fork.c | 3 ++-
 sys/kern/kern_proc.c | 1 +
 sys/sys/proc.h       | 7 +++++++
 4 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/sys/kern/kern_exit.c b/sys/kern/kern_exit.c
index 63e46dcf46f7..2f94386c9101 100644
--- a/sys/kern/kern_exit.c
+++ b/sys/kern/kern_exit.c
@@ -1107,7 +1107,7 @@ proc_reap(struct thread *td, struct proc *p, int *status, int options)
 
 	KASSERT(FIRST_THREAD_IN_PROC(p),
 	    ("proc_reap: no residual thread!"));
-	uma_zfree(proc_zone, p);
+	PROC_TREE_UNREF(p);
 	atomic_add_int(&nprocs, -1);
 }
 
diff --git a/sys/kern/kern_fork.c b/sys/kern/kern_fork.c
index edbb61e0e68b..83a3162d8cfb 100644
--- a/sys/kern/kern_fork.c
+++ b/sys/kern/kern_fork.c
@@ -1058,6 +1058,7 @@ fork1(struct thread *td, struct fork_req *fr)
 		pages = kstack_pages;
 	/* Allocate new proc. */
 	newproc = uma_zalloc(proc_zone, M_WAITOK);
+	PROC_TREE_REF(newproc);
 	td2 = FIRST_THREAD_IN_PROC(newproc);
 	if (td2 == NULL) {
 		td2 = thread_alloc(pages);
@@ -1138,7 +1139,7 @@ fail1:
 fail2:
 	if (vm2 != NULL)
 		vmspace_free(vm2);
-	uma_zfree(proc_zone, newproc);
+	PROC_TREE_UNREF(newproc);
 	if ((flags & RFPROCDESC) != 0 && fp_procdesc != NULL) {
 		fdclose(td, fp_procdesc, *fr->fr_pd_fd);
 		fdrop(fp_procdesc, td);
diff --git a/sys/kern/kern_proc.c b/sys/kern/kern_proc.c
index 758f54c540ab..71d5faf3c050 100644
--- a/sys/kern/kern_proc.c
+++ b/sys/kern/kern_proc.c
@@ -281,6 +281,7 @@ proc_init(void *mem, int size, int flags)
 	p->p_pgrp = NULL;
 	TAILQ_INIT(&p->p_kqtim_stop);
 	STAILQ_INIT(&p->p_ktr);
+	refcount_init(&p->p_tree_refcnt, 0);
 	return (0);
 }
 
diff --git a/sys/sys/proc.h b/sys/sys/proc.h
index 4ad22d46b5bb..fd5c366ab95d 100644
--- a/sys/sys/proc.h
+++ b/sys/sys/proc.h
@@ -779,6 +779,7 @@ struct proc {
 	TAILQ_HEAD(, kq_timer_cb_data)	p_kqtim_stop;	/* (c) */
 	LIST_ENTRY(proc) p_jaillist;	/* (d) Jail process linkage. */
 	u_int		p_asig;		/* (c) ASYNCEXIT pending signal. */
+	u_int		p_tree_refcnt;	/* (e) proctree refcount */
 };
 
 #define	p_session	p_pgrp->pg_session
@@ -804,6 +805,12 @@ struct proc {
 #define	PROC_PROFUNLOCK(p)	mtx_unlock_spin(&(p)->p_profmtx)
 #define	PROC_PROFLOCK_ASSERT(p, type)	mtx_assert(&(p)->p_profmtx, (type))
 
+#define	PROC_TREE_REF(p)	refcount_acquire(&(p)->p_tree_refcnt)
+#define	PROC_TREE_UNREF(p)	do {					\
+	if (refcount_release(&(p)->p_tree_refcnt))			\
+		uma_zfree(proc_zone, p);				\
+} while (0)
+
 /* These flags are kept in p_flag. */
 #define	P_ADVLOCK	0x00000001	/* Process may hold a POSIX advisory
 					   lock. */