[libc-commits] [PATCH] D149790: [libc][rpc] Fix the memory ordering in lock.

[Jon Chesterfield via Phabricator via libc-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rGf152796fd3e0: [libc][rpc] Fix the memory ordering in lock. (authored by JonChesterfield).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D149790/new/

https://reviews.llvm.org/D149790

Files:
  libc/src/__support/RPC/rpc.h


Index: libc/src/__support/RPC/rpc.h
===================================================================
--- libc/src/__support/RPC/rpc.h
+++ libc/src/__support/RPC/rpc.h
@@ -248,6 +248,9 @@
   if (lock->fetch_or(1, cpp::MemoryOrder::RELAXED))
     return cpp::nullopt;
 
+  // The mailbox state must be read with the lock held.
+  atomic_thread_fence(cpp::MemoryOrder::ACQUIRE);
+
   uint32_t in = inbox->load(cpp::MemoryOrder::RELAXED);
   uint32_t out = outbox->load(cpp::MemoryOrder::RELAXED);
 
@@ -285,6 +288,9 @@
   if (lock->fetch_or(1, cpp::MemoryOrder::RELAXED))
     return cpp::nullopt;
 
+  // The mailbox state must be read with the lock held.
+  atomic_thread_fence(cpp::MemoryOrder::ACQUIRE);
+
   in = inbox->load(cpp::MemoryOrder::RELAXED);
   out = outbox->load(cpp::MemoryOrder::RELAXED);
 


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