Merge branch 'master' of https://github.com/grpc/grpc into log_envar
diff --git a/src/core/lib/iomgr/ev_epoll1_linux.cc b/src/core/lib/iomgr/ev_epoll1_linux.cc
index 9e3643f..61da996 100644
--- a/src/core/lib/iomgr/ev_epoll1_linux.cc
+++ b/src/core/lib/iomgr/ev_epoll1_linux.cc
@@ -18,6 +18,8 @@
 
 #include "src/core/lib/iomgr/port.h"
 
+#include <grpc/support/log.h>
+
 /* This polling engine is only relevant on linux kernels supporting epoll() */
 #ifdef GRPC_LINUX_EPOLL
 #include "src/core/lib/iomgr/ev_epoll1_linux.h"
@@ -34,7 +36,6 @@
 
 #include <grpc/support/alloc.h>
 #include <grpc/support/cpu.h>
-#include <grpc/support/log.h>
 #include <grpc/support/string_util.h>
 #include <grpc/support/tls.h>
 #include <grpc/support/useful.h>
@@ -1230,6 +1231,7 @@
  * support is available */
 const grpc_event_engine_vtable* grpc_init_epoll1_linux(bool explicit_request) {
   if (!grpc_has_wakeup_fd()) {
+    gpr_log(GPR_ERROR, "Skipping epoll1 because of no wakeup fd.");
     return NULL;
   }
 
@@ -1254,6 +1256,8 @@
 /* If GRPC_LINUX_EPOLL is not defined, it means epoll is not available. Return
  * NULL */
 const grpc_event_engine_vtable* grpc_init_epoll1_linux(bool explicit_request) {
+  gpr_log(GPR_ERROR,
+          "Skipping epoll1 becuase GRPC_LINUX_EPOLL is not defined.");
   return NULL;
 }
 #endif /* defined(GRPC_POSIX_SOCKET) */
diff --git a/src/core/lib/iomgr/ev_epollex_linux.cc b/src/core/lib/iomgr/ev_epollex_linux.cc
index 26ed1f6..caaee76 100644
--- a/src/core/lib/iomgr/ev_epollex_linux.cc
+++ b/src/core/lib/iomgr/ev_epollex_linux.cc
@@ -18,6 +18,8 @@
 
 #include "src/core/lib/iomgr/port.h"
 
+#include <grpc/support/log.h>
+
 /* This polling engine is only relevant on linux kernels supporting epoll() */
 #ifdef GRPC_LINUX_EPOLL
 
@@ -34,7 +36,6 @@
 #include <unistd.h>
 
 #include <grpc/support/alloc.h>
-#include <grpc/support/log.h>
 #include <grpc/support/string_util.h>
 #include <grpc/support/tls.h>
 #include <grpc/support/useful.h>
@@ -1451,10 +1452,12 @@
   }
 
   if (!grpc_has_wakeup_fd()) {
+    gpr_log(GPR_ERROR, "Skipping epollex because of no wakeup fd.");
     return NULL;
   }
 
   if (!grpc_is_epollexclusive_available()) {
+    gpr_log(GPR_INFO, "Skipping epollex because it is not supported.");
     return NULL;
   }
 
@@ -1480,6 +1483,8 @@
  * NULL */
 const grpc_event_engine_vtable* grpc_init_epollex_linux(
     bool explicitly_requested) {
+  gpr_log(GPR_ERROR,
+          "Skipping epollex becuase GRPC_LINUX_EPOLL is not defined.");
   return NULL;
 }
 #endif /* defined(GRPC_POSIX_SOCKET) */
diff --git a/src/core/lib/iomgr/ev_epollsig_linux.cc b/src/core/lib/iomgr/ev_epollsig_linux.cc
index 9a12780..42806e9 100644
--- a/src/core/lib/iomgr/ev_epollsig_linux.cc
+++ b/src/core/lib/iomgr/ev_epollsig_linux.cc
@@ -19,6 +19,7 @@
 #include "src/core/lib/iomgr/port.h"
 
 #include <grpc/grpc_posix.h>
+#include <grpc/support/log.h>
 
 /* This polling engine is only relevant on linux kernels supporting epoll() */
 #ifdef GRPC_LINUX_EPOLL
@@ -37,7 +38,6 @@
 #include <unistd.h>
 
 #include <grpc/support/alloc.h>
-#include <grpc/support/log.h>
 #include <grpc/support/string_util.h>
 #include <grpc/support/tls.h>
 #include <grpc/support/useful.h>
@@ -1711,14 +1711,17 @@
     bool explicit_request) {
   /* If use of signals is disabled, we cannot use epoll engine*/
   if (is_grpc_wakeup_signal_initialized && grpc_wakeup_signal < 0) {
+    gpr_log(GPR_ERROR, "Skipping epollsig because use of signals is disabled.");
     return NULL;
   }
 
   if (!grpc_has_wakeup_fd()) {
+    gpr_log(GPR_ERROR, "Skipping epollsig because of no wakeup fd.");
     return NULL;
   }
 
   if (!is_epoll_available()) {
+    gpr_log(GPR_ERROR, "Skipping epollsig because epoll is unavailable.");
     return NULL;
   }
 
@@ -1726,6 +1729,8 @@
     if (explicit_request) {
       grpc_use_signal(SIGRTMIN + 6);
     } else {
+      gpr_log(GPR_ERROR,
+              "Skipping epollsig because uninitialized wakeup signal.");
       return NULL;
     }
   }
@@ -1751,6 +1756,8 @@
  * NULL */
 const grpc_event_engine_vtable* grpc_init_epollsig_linux(
     bool explicit_request) {
+  gpr_log(GPR_ERROR,
+          "Skipping epollsig becuase GRPC_LINUX_EPOLL is not defined.");
   return NULL;
 }
 #endif /* defined(GRPC_POSIX_SOCKET) */
diff --git a/src/core/lib/iomgr/ev_poll_posix.cc b/src/core/lib/iomgr/ev_poll_posix.cc
index 554a438..5745a2a 100644
--- a/src/core/lib/iomgr/ev_poll_posix.cc
+++ b/src/core/lib/iomgr/ev_poll_posix.cc
@@ -1712,6 +1712,7 @@
 
 const grpc_event_engine_vtable* grpc_init_poll_posix(bool explicit_request) {
   if (!grpc_has_wakeup_fd()) {
+    gpr_log(GPR_ERROR, "Skipping poll because of no wakeup fd.");
     return NULL;
   }
   if (!GRPC_LOG_IF_ERROR("pollset_global_init", pollset_global_init())) {
diff --git a/src/core/lib/iomgr/ev_posix.cc b/src/core/lib/iomgr/ev_posix.cc
index f72f508..a05279a 100644
--- a/src/core/lib/iomgr/ev_posix.cc
+++ b/src/core/lib/iomgr/ev_posix.cc
@@ -172,12 +172,12 @@
     gpr_free(strings[i]);
   }
   gpr_free(strings);
-  gpr_free(s);
 
   if (g_event_engine == NULL) {
-    gpr_log(GPR_ERROR, "No event engine could be initialized");
+    gpr_log(GPR_ERROR, "No event engine could be initialized from %s", s);
     abort();
   }
+  gpr_free(s);
 }
 
 void grpc_event_engine_shutdown(void) {