[PATCH 5/6] liveupdate: Make unregister functions return void

Pasha Tatashin
2026-03-17T02:51:09Z

Change liveupdate_unregister_file_handler and liveupdate_unregister_flb
to return void instead of an error code. If they fail to unregister
due to dangling references, print a warning instead of aborting.

As pointed out by Jason Gunthorpe and Alex Williamson, returning an error
from a "destroy" or unregister function during a module unload is a poor
API choice since the unload cannot be stopped at that point.

Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
include/linux/liveupdate.h | 13 ++++++------
kernel/liveupdate/luo_file.c | 27 +++++++++++-------------
kernel/liveupdate/luo_flb.c | 40 ++++++++++--------------------------
lib/tests/liveupdate.c | 8 ++------
4 files changed, 31 insertions(+), 57 deletions(-)

diff --git a/include/linux/liveupdate.h b/include/linux/liveupdate.h
index 8394fb2d8774..293df26b9e7f 100644
--- a/include/linux/liveupdate.h
+++ b/include/linux/liveupdate.h
@@ -231,12 +231,12 @@ bool liveupdate_enabled(void);
int liveupdate_reboot(void);

int liveupdate_register_file_handler(struct liveupdate_file_handler *fh);
-int liveupdate_unregister_file_handler(struct liveupdate_file_handler *fh);
+void liveupdate_unregister_file_handler(struct liveupdate_file_handler *fh);

int liveupdate_register_flb(struct liveupdate_file_handler *fh,
struct liveupdate_flb *flb);
-int liveupdate_unregister_flb(struct liveupdate_file_handler *fh,
- struct liveupdate_flb *flb);
+void liveupdate_unregister_flb(struct liveupdate_file_handler *fh,
+ struct liveupdate_flb *flb);

int liveupdate_flb_get_incoming(struct liveupdate_flb *flb, void **objp);
int liveupdate_flb_get_outgoing(struct liveupdate_flb *flb, void **objp);
@@ -258,9 +258,8 @@ static inline int liveupdate_register_file_handler(struct liveupdate_file_handle
return -EOPNOTSUPP;
}

-static inline int liveupdate_unregister_file_handler(struct liveupdate_file_handler *fh)
+static inline void liveupdate_unregister_file_handler(struct liveupdate_file_handler *fh)
{
- return -EOPNOTSUPP;
}

static inline int liveupdate_register_flb(struct liveupdate_file_handler *fh,
@@ -269,8 +268,8 @@ static inline int liveupdate_register_flb(struct liveupdate_file_handler *fh,
return -EOPNOTSUPP;
}

-static inline int liveupdate_unregister_flb(struct liveupdate_file_handler *fh,
- struct liveupdate_flb *flb)
+static inline void liveupdate_unregister_flb(struct liveupdate_file_handler *fh,
+ struct liveupdate_flb *flb)
{
return -EOPNOTSUPP;
}
diff --git a/kernel/liveupdate/luo_file.c b/kernel/liveupdate/luo_file.c
index 6b2b49cb375e..0fe2f8be8bd1 100644
--- a/kernel/liveupdate/luo_file.c
+++ b/kernel/liveupdate/luo_file.c
@@ -907,21 +907,17 @@ int liveupdate_register_file_handler(struct liveupdate_file_handler *fh)
* reverses the operations of liveupdate_register_file_handler().
*
* It ensures safe removal by checking that:
- * No live update session is currently in progress.
* No FLB registered with this file handler.
*
* If the unregistration fails, the internal test state is reverted.
*
- * Return: 0 Success. -EOPNOTSUPP when live update is not enabled. -EBUSY A live
- * update is in progress, can't quiesce live update or FLB is registred with
- * this file handler.
*/
-int liveupdate_unregister_file_handler(struct liveupdate_file_handler *fh)
+void liveupdate_unregister_file_handler(struct liveupdate_file_handler *fh)
{
- int err = -EBUSY;
+ bool is_empty;

if (!liveupdate_enabled())
- return -EOPNOTSUPP;
+ return;

liveupdate_test_unregister(fh);

@@ -929,18 +925,19 @@ int liveupdate_unregister_file_handler(struct liveupdate_file_handler *fh)
goto err_register;

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

- return 0;
+ if (!is_empty) {
+ pr_warn("Failed to unregister file handler '%s': FLB list not empty\n",
+ fh->compatible);
+ liveupdate_test_register(fh);
+ }
+ return;

-err_resume:
- luo_session_resume();
err_register:
liveupdate_test_register(fh);
- return err;
}
diff --git a/kernel/liveupdate/luo_flb.c b/kernel/liveupdate/luo_flb.c
index daa852abdedd..23fa6e0c6083 100644
--- a/kernel/liveupdate/luo_flb.c
+++ b/kernel/liveupdate/luo_flb.c
@@ -436,31 +436,17 @@ int liveupdate_register_flb(struct liveupdate_file_handler *fh,
* the FLB is removed from the global registry and the reference to its
* owner module (acquired during registration) is released.
*
- * Context: This function ensures the session is quiesced (no active FDs
- * being created) during the update. It is typically called from a
- * subsystem's module exit function.
- * Return: 0 on success.
- * -EOPNOTSUPP if live update is disabled.
- * -EBUSY if the live update session is active and cannot be quiesced.
- * -ENOENT if the FLB was not found in the file handler's list.
*/
-int liveupdate_unregister_flb(struct liveupdate_file_handler *fh,
- struct liveupdate_flb *flb)
+void liveupdate_unregister_flb(struct liveupdate_file_handler *fh,
+ struct liveupdate_flb *flb)
{
struct luo_flb_private *private = luo_flb_get_private(flb);
struct list_head *flb_list = &ACCESS_PRIVATE(fh, flb_list);
struct luo_flb_link *iter;
- int err = -ENOENT;
+ bool found = false;

if (!liveupdate_enabled())
- return -EOPNOTSUPP;
-
- /*
- * Ensure the system is quiescent (no active sessions).
- * This acts as a global lock for unregistration.
- */
- if (!luo_session_quiesce())
- return -EBUSY;
+ return;

guard(rwsem_write)(&luo_flb_lock);
guard(rwsem_write)(&ACCESS_PRIVATE(fh, flb_lock));
@@ -470,15 +456,19 @@ int liveupdate_unregister_flb(struct liveupdate_file_handler *fh,
if (iter->flb == flb) {
list_del(&iter->list);
kfree(iter);
- err = 0;
+ found = true;
break;
}
}

- if (err)
- goto err_resume;
+ if (!found) {
+ pr_warn("Failed to unregister FLB '%s': not found in file handler '%s'\n",
+ flb->compatible, fh->compatible);
+ return;
+ }

private->users--;
+
/*
* If this is the last file-handler with which we are registred, remove
* from the global list, and relese module reference.
@@ -487,14 +477,6 @@ int liveupdate_unregister_flb(struct liveupdate_file_handler *fh,
list_del_init(&private->list);
luo_flb_global.count--;
}
-
- luo_session_resume();
-
- return 0;
-
-err_resume:
- luo_session_resume();
- return err;
}

/**
diff --git a/lib/tests/liveupdate.c b/lib/tests/liveupdate.c
index 496d6ef91a30..5b6abf779f87 100644
--- a/lib/tests/liveupdate.c
+++ b/lib/tests/liveupdate.c
@@ -137,16 +137,12 @@ void liveupdate_test_register(struct liveupdate_file_handler *fh)

void liveupdate_test_unregister(struct liveupdate_file_handler *fh)
{
- int err, i;
+ int i;

for (i = 0; i < TEST_NFLBS; i++) {
struct liveupdate_flb *flb = &test_flbs[i];

- err = liveupdate_unregister_flb(fh, flb);
- if (err) {
- pr_err("Failed to unregister %s %pe\n",
- flb->compatible, ERR_PTR(err));
- }
+ liveupdate_unregister_flb(fh, flb);
}

pr_info("Unregistered %d FLBs from file handler: [%s]\n",
--
2.53.0.851.ga537e3e6e9-goog