[PATCH 19/49] x86/alternatives: Add text_mutex) assert to smp_text_poke_batch_flush()

[Ingo Molnar]

It's possible to escape the text_mutex-held assert in
smp_text_poke_batch_process() if the caller uses a properly
batched and sorted series of patch requests, so add
an explicit lockdep_assert_held() to make sure it's
held by all callers.

All text_poke_int3_*() APIs will call either smp_text_poke_batch_process()
or smp_text_poke_batch_flush() internally.

The text_mutex must be held, because tp_vec and tp_vec_nr et al
are all globals, and the INT3 patching machinery itself relies on
external serialization.

Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 arch/x86/kernel/alternative.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index be836d1f6d99..378db5f0b59b 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -2860,6 +2860,8 @@ static bool tp_order_fail(void *addr)
 
 static void smp_text_poke_batch_flush(void *addr)
 {
+	lockdep_assert_held(&text_mutex);
+
 	if (tp_vec_nr == TP_VEC_MAX || tp_order_fail(addr)) {
 		smp_text_poke_batch_process(tp_vec, tp_vec_nr);
 		tp_vec_nr = 0;
-- 
2.45.2