Merge bitcoin/bitcoin#24931: Strengthen thread safety assertions

ce893c0497fc9b8ab9752153dfcc77c9f427545e doc: Update developer notes (Anthony Towns)
d2852917eecad6ab422a7b2c9892d351a7f0cc96 sync.h: Imply negative assertions when calling LOCK (Anthony Towns)
bba87c0553780eacf0317fbfec7330ea27aa02f8 scripted-diff: Convert global Mutexes to GlobalMutexes (Anthony Towns)
a559509a0b8cade27199740212d7b589f71a0e3b sync.h: Add GlobalMutex type (Anthony Towns)
be6aa72f9f8d50b6b5b19b319a74abe7ab4099ff qt/clientmodel: thread safety annotation for m_cached_tip_mutex (Anthony Towns)
f24bd45b37e1b2d19e5a053dbfefa30306c1d41a net_processing: thread safety annotation for m_tx_relay_mutex (Anthony Towns)

Pull request description:

  This changes `LOCK(mutex)` for non-global, non-recursive mutexes to be annotated with the negative capability for the mutex it refers to, to prevent . clang applies negative capabilities recursively, so this helps avoid forgetting to annotate functions.

  This can't reasonably be used for globals, because clang would require every function to be annotated with `EXCLUSIVE_LOCKS_REQUIRED(!g_mutex)` for each global mutex; so this introduces a trivial `GlobalMutex` subclass of `Mutex`, and reduces the annotations for both `GlobalMutex`  to `LOCKS_EXCLUDED` which only catches trivial errors (eg (`LOCK(x); LOCK(x);`).

ACKs for top commit:
  MarcoFalke:
    review ACK ce893c0497fc9b8ab9752153dfcc77c9f427545e 🐦
  hebasto:
    ACK ce893c0497fc9b8ab9752153dfcc77c9f427545e

Tree-SHA512: 5c35e8c7677ce3d994a7e3774f4344adad496223a51b3a1d1d3b5f20684b2e1d5cff688eb3fbc8d33e1b9940dfa76e515f9434e21de6f3ce3c935e29a319f529

1 files changed, 1 insertions, 1 deletions

diff --git a/src/net_processing.cpp b/src/net_processing.cpp
index 30d5548385..1d69975f55 100644
--- a/src/net_processing.cpp
+++ b/src/net_processing.cpp
@@ -292,7 +292,7 @@ struct Peer {
         return m_tx_relay.get();
     };
 
-    TxRelay* GetTxRelay()
+    TxRelay* GetTxRelay() EXCLUSIVE_LOCKS_REQUIRED(!m_tx_relay_mutex)
     {
         return WITH_LOCK(m_tx_relay_mutex, return m_tx_relay.get());
     };