[PATCH v4 07/13] powerpc/rtas: Warn if per-function lock isn't held

[Nathan Lynch via B4 Relay]

From: Nathan Lynch <nath...@linux.ibm.com>

If the function descriptor has a populated lock member, then callers
are required to hold it across calls. Now that the firmware activation
sequence is appropriately guarded, we can warn when the requirement
isn't satisfied.

__do_enter_rtas_trace() gets reorganized a bit as a result of
performing the function descriptor lookup unconditionally now.

Signed-off-by: Nathan Lynch <nath...@linux.ibm.com>
---
 arch/powerpc/kernel/rtas.c | 21 +++++++++------------
 1 file changed, 9 insertions(+), 12 deletions(-)

diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
index e38ba05ad613..deb6289fcf9c 100644
--- a/arch/powerpc/kernel/rtas.c
+++ b/arch/powerpc/kernel/rtas.c
@@ -685,28 +685,25 @@ static void __do_enter_rtas(struct rtas_args *args)
 
 static void __do_enter_rtas_trace(struct rtas_args *args)
 {
-       const char *name = NULL;
+       struct rtas_function *func = 
rtas_token_to_function(be32_to_cpu(args->token));
 
-       if (args == &rtas_args)
-               lockdep_assert_held(&rtas_lock);
        /*
-        * If the tracepoints that consume the function name aren't
-        * active, avoid the lookup.
+        * If there is a per-function lock, it must be held by the
+        * caller.
         */
-       if ((trace_rtas_input_enabled() || trace_rtas_output_enabled())) {
-               const s32 token = be32_to_cpu(args->token);
-               const struct rtas_function *func = 
rtas_token_to_function(token);
+       if (func->lock)
+               WARN_ON(!mutex_is_locked(func->lock));
 
-               name = func->name;
-       }
+       if (args == &rtas_args)
+               lockdep_assert_held(&rtas_lock);
 
-       trace_rtas_input(args, name);
+       trace_rtas_input(args, func->name);
        trace_rtas_ll_entry(args);
 
        __do_enter_rtas(args);
 
        trace_rtas_ll_exit(args);
-       trace_rtas_output(args, name);
+       trace_rtas_output(args, func->name);
 }
 
 static void do_enter_rtas(struct rtas_args *args)

-- 
2.41.0