[compiler-rt] [ASan] Prevent ASan/LSan deadlock by preloading modules before error reporting (PR #131756)

[via llvm-commits]

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@@ -126,6 +126,27 @@ class ScopedInErrorReport {
  public:
   explicit ScopedInErrorReport(bool fatal = false)
       : halt_on_error_(fatal || flags()->halt_on_error) {
+   /*
+    * Deadlock Prevention Between ASan and LSan
+    *
+    * Background:
+    * - The `dl_iterate_phdr` function requires holding libdl's internal lock (Lock A).
+    * - LSan acquires the ASan thread registry lock (Lock B) *after* calling `dl_iterate_phdr`.
+    *
+    * Problem Scenario:
+    * When ASan attempts to call `dl_iterate_phdr` while holding Lock B (e.g., during
+    * error reporting via `ErrorDescription::Print`), a circular lock dependency may occur:
+    *   1. Thread 1: Holds Lock B → Requests Lock A (via dl_iterate_phdr)
+    *   2. Thread 2: Holds Lock A → Requests Lock B (via LSan operations)
+    *
+    * Solution:
+    * Proactively load all required modules before acquiring Lock B. This ensures:
+    * 1. Any `dl_iterate_phdr` calls during module loading complete before locking
+    * 2. Subsequent error reporting avoids nested lock acquisition patterns
+    * 3. Eliminates the lock order inversion risk between libdl and ASan's thread registry
+    */
+    Symbolizer::GetOrInit()->GetRefreshedListOfModules();
----------------
Camsyn wrote:

When multiple ASan threads fire an error simultaneously, the concurrency problem of loading modules does occur.

Maybe we should hold the lock of `Symbolizer` while calling `GetRefreshedListOfModules()`? 
However, there is no exposed interface to obtain `Symbolizer`'s inner lock just like `asanThreadRegistry().lock()`. `Symbolizer` seems to only lock the inner mutex by parts of its public methods, e.g., `SymbolizeXXX`, which unfortunately do not include `GetRefreshedListOfModules()`.

However, the current context still exists an accessible lock `static Mutex error_message_buf_mutex`, we can trickily tackle the above concurrency problem by locking it, although this is not very suitable for the original purpose of the lock (for "error message buf").

https://github.com/llvm/llvm-project/pull/131756