From: John Salem <josalem@microsoft.com>
Date: Thu, 30 May 2019 01:59:27 +0000 (-0700)
Subject: Add COMPlus_LTTng environment variable (#24733)
X-Git-Tag: accepted/tizen/unified/20190813.215958~42^2~30
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=cc1f8ab68e645cd46601b1df50ff644dfffc4dae;p=platform%2Fupstream%2Fcoreclr.git

Add COMPlus_LTTng environment variable (#24733)

* default value is 1, and when set to 0 will disable loading LTTng.

Co-Authored-By: Jan Kotas <jkotas@microsoft.com>
---

diff --git a/src/inc/clrconfigvalues.h b/src/inc/clrconfigvalues.h
index ab28104..c995e6e 100644
--- a/src/inc/clrconfigvalues.h
+++ b/src/inc/clrconfigvalues.h
@@ -248,6 +248,10 @@ CONFIG_DWORD_INFO_DIRECT_ACCESS(INTERNAL_SuppressChecks, W("SuppressChecks"), ""
 CONFIG_DWORD_INFO(INTERNAL_SuppressLockViolationsOnReentryFromOS, W("SuppressLockViolationsOnReentryFromOS"), 0, "64 bit OOM tests re-enter the CLR via RtlVirtualUnwind.  This indicates whether to suppress resulting locking violations.")
 #endif // WIN64EXCEPTIONS
 
+///
+/// Diagnostics (unsuported general-purpose)
+///
+RETAIL_CONFIG_DWORD_INFO(UNSUPORTED_LTTng, W("LTTng"), 1, "If COMPlus_LTTng is set to 0, this will prevent the LTTng library from being loaded at runtime")
 
 ///
 /// Exception Handling
diff --git a/src/pal/src/misc/tracepointprovider.cpp b/src/pal/src/misc/tracepointprovider.cpp
index 8d20266..6aa8fb5 100644
--- a/src/pal/src/misc/tracepointprovider.cpp
+++ b/src/pal/src/misc/tracepointprovider.cpp
@@ -59,6 +59,16 @@ __attribute__((constructor (200)))
 static void
 PAL_InitializeTracing(void)
 {
+    int fShouldLoad = 1;
+    // Check if loading the LTTng providers should be disabled.
+    // Note: this env var is formally declared in clrconfigvalues.h, but
+    // this code is executed too early to use the mechanics that come with that definition.
+    char *disableValue = getenv("COMPlus_LTTng");
+    if (disableValue != NULL)
+    {
+        fShouldLoad = strtol(disableValue, NULL, 10);
+    }
+
     // Get the path to the currently executing shared object (libcoreclr.so).
     Dl_info info;
     int succeeded = dladdr((void *)PAL_InitializeTracing, &info);
@@ -99,11 +109,13 @@ PAL_InitializeTracing(void)
         return;
     }
     
-
-
-    // Load the tracepoint provider.
-    // It's OK if this fails - that just means that tracing dependencies aren't available.
-    dlopen(tpProvPath, RTLD_NOW | RTLD_GLOBAL);
+    
+    if (fShouldLoad)
+    {
+        // Load the tracepoint provider.
+        // It's OK if this fails - that just means that tracing dependencies aren't available.
+        dlopen(tpProvPath, RTLD_NOW | RTLD_GLOBAL);
+    }
 }
 
 #endif