scftorture: Use workqueue to free scf_check
Paul reported an invalid wait context issue in scftorture catched by
lockdep, and the cause of the issue is because scf_handler() may call
kfree() to free the struct scf_check:
static void scf_handler(void *scfc_in)
{
[...]
} else {
kfree(scfcp);
}
}
(call chain anlysis from Marco Elver)
This is problematic because smp_call_function() uses non-threaded
interrupt and kfree() may acquire a local_lock which is a sleepable lock
on RT.
The general rule is: do not alloc or free memory in non-threaded
interrupt conntexts.
A quick fix is to use workqueue to defer the kfree(). However, this is
OK only because scftorture is test code. In general the users of
interrupts should avoid giving interrupt handlers the ownership of
objects, that is, users should handle the lifetime of objects outside
and interrupt handlers should only hold references to objects.
Reported-by: "Paul E. McKenney" <paulmck@kernel.org>
Link: https://lore.kernel.org/lkml/41619255-cdc2-4573-a360-7794fc3614f7@paulmck-laptop/
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
1 file changed
