From e7995f213c90ec4e0b1159cb630d6ca9761ee35a Mon Sep 17 00:00:00 2001
From: Ara Ayvazyan <Aivazyan@microsoft.com>
Date: Wed, 4 Apr 2018 17:37:40 -0700
Subject: [PATCH] Avoid low severity log message construction

---
 include/grpc/support/log.h      |  2 ++
 src/core/lib/gpr/log.cc         | 10 ++++++++--
 src/core/lib/gpr/log_android.cc |  4 ++++
 src/core/lib/gpr/log_linux.cc   |  4 ++++
 src/core/lib/gpr/log_posix.cc   |  4 ++++
 src/core/lib/gpr/log_windows.cc |  5 +++++
 6 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/include/grpc/support/log.h b/include/grpc/support/log.h
index 2236703db35..7521453b80e 100644
--- a/include/grpc/support/log.h
+++ b/include/grpc/support/log.h
@@ -61,6 +61,8 @@ GPRAPI const char* gpr_log_severity_string(gpr_log_severity severity);
 GPRAPI void gpr_log(const char* file, int line, gpr_log_severity severity,
                     const char* format, ...) GPR_PRINT_FORMAT_CHECK(4, 5);
 
+GPRAPI int gpr_should_log(gpr_log_severity severity);
+
 GPRAPI void gpr_log_message(const char* file, int line,
                             gpr_log_severity severity, const char* message);
 
diff --git a/src/core/lib/gpr/log.cc b/src/core/lib/gpr/log.cc
index 72787ab7240..01ef112fb31 100644
--- a/src/core/lib/gpr/log.cc
+++ b/src/core/lib/gpr/log.cc
@@ -44,10 +44,16 @@ const char* gpr_log_severity_string(gpr_log_severity severity) {
   GPR_UNREACHABLE_CODE(return "UNKNOWN");
 }
 
+int gpr_should_log(gpr_log_severity severity) {
+  return static_cast<gpr_atm>(severity) >=
+                 gpr_atm_no_barrier_load(&g_min_severity_to_print)
+             ? 1
+             : 0;
+}
+
 void gpr_log_message(const char* file, int line, gpr_log_severity severity,
                      const char* message) {
-  if (static_cast<gpr_atm>(severity) <
-      gpr_atm_no_barrier_load(&g_min_severity_to_print)) {
+  if (gpr_should_log(severity) == 0) {
     return;
   }
 
diff --git a/src/core/lib/gpr/log_android.cc b/src/core/lib/gpr/log_android.cc
index 0d3ac0fe522..40ef4c640da 100644
--- a/src/core/lib/gpr/log_android.cc
+++ b/src/core/lib/gpr/log_android.cc
@@ -41,6 +41,10 @@ static android_LogPriority severity_to_log_priority(gpr_log_severity severity) {
 
 void gpr_log(const char* file, int line, gpr_log_severity severity,
              const char* format, ...) {
+  /* Avoid message construction if gpr_log_message won't log */
+  if (gpr_should_log(severity) == 0) {
+    return;
+  }
   char* message = NULL;
   va_list args;
   va_start(args, format);
diff --git a/src/core/lib/gpr/log_linux.cc b/src/core/lib/gpr/log_linux.cc
index e4417d9d5d4..561276f0c20 100644
--- a/src/core/lib/gpr/log_linux.cc
+++ b/src/core/lib/gpr/log_linux.cc
@@ -44,6 +44,10 @@ static long gettid(void) { return syscall(__NR_gettid); }
 
 void gpr_log(const char* file, int line, gpr_log_severity severity,
              const char* format, ...) {
+  /* Avoid message construction if gpr_log_message won't log */
+  if (gpr_should_log(severity) == 0) {
+    return;
+  }
   char* message = nullptr;
   va_list args;
   va_start(args, format);
diff --git a/src/core/lib/gpr/log_posix.cc b/src/core/lib/gpr/log_posix.cc
index 6f93cdefcdf..0acb2255724 100644
--- a/src/core/lib/gpr/log_posix.cc
+++ b/src/core/lib/gpr/log_posix.cc
@@ -34,6 +34,10 @@ static intptr_t gettid(void) { return (intptr_t)pthread_self(); }
 
 void gpr_log(const char* file, int line, gpr_log_severity severity,
              const char* format, ...) {
+  /* Avoid message construction if gpr_log_message won't log */
+  if (gpr_should_log(severity) == 0) {
+    return;
+  }
   char buf[64];
   char* allocated = nullptr;
   char* message = nullptr;
diff --git a/src/core/lib/gpr/log_windows.cc b/src/core/lib/gpr/log_windows.cc
index caaa973f5a8..060be572b80 100644
--- a/src/core/lib/gpr/log_windows.cc
+++ b/src/core/lib/gpr/log_windows.cc
@@ -34,6 +34,11 @@
 
 void gpr_log(const char* file, int line, gpr_log_severity severity,
              const char* format, ...) {
+  /* Avoid message construction if gpr_log_message won't log */
+  if (gpr_should_log(severity) == 0) {
+    return;
+  }
+
   char* message = NULL;
   va_list args;
   int ret;