[PATCH 6/6] liveupdate: Remove luo_session_quiesce()

Pasha Tatashin
2026-03-17T02:51:11Z

Now that module references properly handle the usage of file handlers
and FLBs during active sessions, we can safely remove the
luo_session_quiesce() and luo_session_resume() mechanism.

Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
kernel/liveupdate/luo_file.c | 31 +++-------------------
kernel/liveupdate/luo_flb.c | 31 +++++-----------------
kernel/liveupdate/luo_internal.h | 2 --
kernel/liveupdate/luo_session.c | 44 --------------------------------
4 files changed, 9 insertions(+), 99 deletions(-)

diff --git a/kernel/liveupdate/luo_file.c b/kernel/liveupdate/luo_file.c
index 0fe2f8be8bd1..bfa0b4868746 100644
--- a/kernel/liveupdate/luo_file.c
+++ b/kernel/liveupdate/luo_file.c
@@ -847,7 +847,6 @@ void luo_file_set_destroy(struct luo_file_set *file_set)
int liveupdate_register_file_handler(struct liveupdate_file_handler *fh)
{
struct liveupdate_file_handler *fh_iter;
- int err;

if (!liveupdate_enabled())
return -EOPNOTSUPP;
@@ -858,45 +857,29 @@ int liveupdate_register_file_handler(struct liveupdate_file_handler *fh)
return -EINVAL;
}

- /*
- * Ensure the system is quiescent (no active sessions).
- * This prevents registering new handlers while sessions are active or
- * while deserialization is in progress.
- */
- if (!luo_session_quiesce())
- return -EBUSY;
-
scoped_guard(rwsem_write, &luo_file_handler_lock) {
/* Check for duplicate compatible strings */
list_private_for_each_entry(fh_iter, &luo_file_handler_list, list) {
if (!strcmp(fh_iter->compatible, fh->compatible)) {
pr_err("File handler registration failed: Compatible string '%s' already registered.\n",
fh->compatible);
- err = -EEXIST;
- goto err_resume;
+ return -EEXIST;
}
}

/* Pin the module implementing the handler */
- if (!try_module_get(fh->ops->owner)) {
- err = -EAGAIN;
- goto err_resume;
- }
+ if (!try_module_get(fh->ops->owner))
+ return -EAGAIN;

INIT_LIST_HEAD(&ACCESS_PRIVATE(fh, flb_list));
init_rwsem(&ACCESS_PRIVATE(fh, flb_lock));
INIT_LIST_HEAD(&ACCESS_PRIVATE(fh, list));
list_add_tail(&ACCESS_PRIVATE(fh, list), &luo_file_handler_list);
}
- luo_session_resume();

liveupdate_test_register(fh);

return 0;
-
-err_resume:
- luo_session_resume();
- return err;
}

/**
@@ -921,23 +904,15 @@ void liveupdate_unregister_file_handler(struct liveupdate_file_handler *fh)

liveupdate_test_unregister(fh);

- if (!luo_session_quiesce())
- goto err_register;
-
scoped_guard(rwsem_write, &luo_file_handler_lock) {
is_empty = list_empty(&ACCESS_PRIVATE(fh, flb_list));
if (is_empty)
list_del(&ACCESS_PRIVATE(fh, list));
}
- luo_session_resume();

if (!is_empty) {
pr_warn("Failed to unregister file handler '%s': FLB list not empty\n",
fh->compatible);
liveupdate_test_register(fh);
}
- return;
-
-err_register:
- liveupdate_test_register(fh);
}
diff --git a/kernel/liveupdate/luo_flb.c b/kernel/liveupdate/luo_flb.c
index 23fa6e0c6083..8810595c672d 100644
--- a/kernel/liveupdate/luo_flb.c
+++ b/kernel/liveupdate/luo_flb.c
@@ -346,7 +346,6 @@ int liveupdate_register_flb(struct liveupdate_file_handler *fh,
struct luo_flb_link *link __free(kfree) = NULL;
struct liveupdate_flb *gflb;
struct luo_flb_link *iter;
- int err;

if (!liveupdate_enabled())
return -EOPNOTSUPP;
@@ -367,22 +366,13 @@ int liveupdate_register_flb(struct liveupdate_file_handler *fh,
if (!link)
return -ENOMEM;

- /*
- * Ensure the system is quiescent (no active sessions).
- * This acts as a global lock for registration: no other thread can
- * be in this section, and no sessions can be creating/using FDs.
- */
- if (!luo_session_quiesce())
- return -EBUSY;
-
guard(rwsem_write)(&luo_flb_lock);
guard(rwsem_write)(&ACCESS_PRIVATE(fh, flb_lock));

/* Check that this FLB is not already linked to this file handler */
- err = -EEXIST;
list_for_each_entry(iter, flb_list, list) {
if (iter->flb == flb)
- goto err_resume;
+ return -EEXIST;
}

/*
@@ -390,20 +380,16 @@ int liveupdate_register_flb(struct liveupdate_file_handler *fh,
* is registered
*/
if (!private->users) {
- if (WARN_ON(!list_empty(&private->list))) {
- err = -EINVAL;
- goto err_resume;
- }
+ if (WARN_ON(!list_empty(&private->list)))
+ return -EINVAL;

- if (luo_flb_global.count == LUO_FLB_MAX) {
- err = -ENOSPC;
- goto err_resume;
- }
+ if (luo_flb_global.count == LUO_FLB_MAX)
+ return -ENOSPC;

/* Check that compatible string is unique in global list */
list_private_for_each_entry(gflb, &luo_flb_global.list, private.list) {
if (!strcmp(gflb->compatible, flb->compatible))
- goto err_resume;
+ return -EEXIST;
}

list_add_tail(&private->list, &luo_flb_global.list);
@@ -414,13 +400,8 @@ int liveupdate_register_flb(struct liveupdate_file_handler *fh,
private->users++;
link->flb = flb;
list_add_tail(&no_free_ptr(link)->list, flb_list);
- luo_session_resume();

return 0;
-
-err_resume:
- luo_session_resume();
- return err;
}

/**
diff --git a/kernel/liveupdate/luo_internal.h b/kernel/liveupdate/luo_internal.h
index 8083d8739b09..ec949f91c8c1 100644
--- a/kernel/liveupdate/luo_internal.h
+++ b/kernel/liveupdate/luo_internal.h
@@ -83,8 +83,6 @@ int __init luo_session_setup_outgoing(void *fdt);
int __init luo_session_setup_incoming(void *fdt);
int luo_session_serialize(void);
int luo_session_deserialize(void);
-bool luo_session_quiesce(void);
-void luo_session_resume(void);

int luo_preserve_file(struct luo_file_set *file_set, u64 token, int fd);
void luo_file_unpreserve_files(struct luo_file_set *file_set);
diff --git a/kernel/liveupdate/luo_session.c b/kernel/liveupdate/luo_session.c
index 783677295640..067ffb54c36a 100644
--- a/kernel/liveupdate/luo_session.c
+++ b/kernel/liveupdate/luo_session.c
@@ -600,47 +600,3 @@ int luo_session_serialize(void)

return err;
}
-
-/**
- * luo_session_quiesce - Ensure no active sessions exist and lock session lists.
- *
- * Acquires exclusive write locks on both incoming and outgoing session lists.
- * It then validates no sessions exist in either list.
- *
- * This mechanism is used during file handler un/registration to ensure that no
- * sessions are currently using the handler, and no new sessions can be created
- * while un/registration is in progress.
- *
- * This prevents registering new handlers while sessions are active or
- * while deserialization is in progress.
- *
- * Return:
- * true - System is quiescent (0 sessions) and locked.
- * false - Active sessions exist. The locks are released internally.
- */
-bool luo_session_quiesce(void)
-{
- down_write(&luo_session_global.incoming.rwsem);
- down_write(&luo_session_global.outgoing.rwsem);
-
- if (luo_session_global.incoming.count ||
- luo_session_global.outgoing.count) {
- up_write(&luo_session_global.outgoing.rwsem);
- up_write(&luo_session_global.incoming.rwsem);
- return false;
- }
-
- return true;
-}
-
-/**
- * luo_session_resume - Unlock session lists and resume normal activity.
- *
- * Releases the exclusive locks acquired by a successful call to
- * luo_session_quiesce().
- */
-void luo_session_resume(void)
-{
- up_write(&luo_session_global.outgoing.rwsem);
- up_write(&luo_session_global.incoming.rwsem);
-}
--
2.53.0.851.ga537e3e6e9-goog