From fecba535d99ec2c819a0d26707047bf2f2f323fa Mon Sep 17 00:00:00 2001
From: "Mark D. Roth" <roth@google.com>
Date: Fri, 17 Mar 2017 09:50:48 -0700
Subject: [PATCH] Switch to using a CAS loop to update the token value.
---
BUILD | 1 +
CMakeLists.txt | 1 +
Makefile | 1 +
binding.gyp | 1 +
build.yaml | 1 +
config.m4 | 1 +
gRPC-Core.podspec | 1 +
grpc.gemspec | 1 +
include/grpc/impl/codegen/atm.h | 5 ++
package.xml | 1 +
src/core/ext/client_channel/retry_throttle.c | 36 +++-----------
src/core/lib/support/atm.c | 47 +++++++++++++++++++
src/python/grpcio/grpc_core_dependencies.py | 1 +
tools/doxygen/Doxyfile.core.internal | 1 +
.../generated/sources_and_headers.json | 1 +
vsprojects/vcxproj/gpr/gpr.vcxproj | 2 +
vsprojects/vcxproj/gpr/gpr.vcxproj.filters | 3 ++
17 files changed, 75 insertions(+), 30 deletions(-)
create mode 100644 src/core/lib/support/atm.c
diff --git a/BUILD b/BUILD
index 4e1f20c3b2..1fe72c02db 100644
--- a/BUILD
+++ b/BUILD
@@ -309,6 +309,7 @@ grpc_cc_library(
"src/core/lib/profiling/basic_timers.c",
"src/core/lib/profiling/stap_timers.c",
"src/core/lib/support/alloc.c",
+ "src/core/lib/support/atm.c",
"src/core/lib/support/avl.c",
"src/core/lib/support/backoff.c",
"src/core/lib/support/cmdline.c",
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8bc07255f1..9e99062f58 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -693,6 +693,7 @@ add_library(gpr
src/core/lib/profiling/basic_timers.c
src/core/lib/profiling/stap_timers.c
src/core/lib/support/alloc.c
+ src/core/lib/support/atm.c
src/core/lib/support/avl.c
src/core/lib/support/backoff.c
src/core/lib/support/cmdline.c
diff --git a/Makefile b/Makefile
index 11bac54c79..2f7120987a 100644
--- a/Makefile
+++ b/Makefile
@@ -2599,6 +2599,7 @@ LIBGPR_SRC = \
src/core/lib/profiling/basic_timers.c \
src/core/lib/profiling/stap_timers.c \
src/core/lib/support/alloc.c \
+ src/core/lib/support/atm.c \
src/core/lib/support/avl.c \
src/core/lib/support/backoff.c \
src/core/lib/support/cmdline.c \
diff --git a/binding.gyp b/binding.gyp
index f6a04b27f9..1107f31889 100644
--- a/binding.gyp
+++ b/binding.gyp
@@ -544,6 +544,7 @@
'src/core/lib/profiling/basic_timers.c',
'src/core/lib/profiling/stap_timers.c',
'src/core/lib/support/alloc.c',
+ 'src/core/lib/support/atm.c',
'src/core/lib/support/avl.c',
'src/core/lib/support/backoff.c',
'src/core/lib/support/cmdline.c',
diff --git a/build.yaml b/build.yaml
index ae546cbb30..7b27968c61 100644
--- a/build.yaml
+++ b/build.yaml
@@ -101,6 +101,7 @@ filegroups:
- src/core/lib/profiling/basic_timers.c
- src/core/lib/profiling/stap_timers.c
- src/core/lib/support/alloc.c
+ - src/core/lib/support/atm.c
- src/core/lib/support/avl.c
- src/core/lib/support/backoff.c
- src/core/lib/support/cmdline.c
diff --git a/config.m4 b/config.m4
index 5eaf161f09..010401f2fb 100644
--- a/config.m4
+++ b/config.m4
@@ -39,6 +39,7 @@ if test "$PHP_GRPC" != "no"; then
src/core/lib/profiling/basic_timers.c \
src/core/lib/profiling/stap_timers.c \
src/core/lib/support/alloc.c \
+ src/core/lib/support/atm.c \
src/core/lib/support/avl.c \
src/core/lib/support/backoff.c \
src/core/lib/support/cmdline.c \
diff --git a/gRPC-Core.podspec b/gRPC-Core.podspec
index 2fb00a3afe..c78e4a7023 100644
--- a/gRPC-Core.podspec
+++ b/gRPC-Core.podspec
@@ -211,6 +211,7 @@ Pod::Spec.new do |s|
'src/core/lib/profiling/basic_timers.c',
'src/core/lib/profiling/stap_timers.c',
'src/core/lib/support/alloc.c',
+ 'src/core/lib/support/atm.c',
'src/core/lib/support/avl.c',
'src/core/lib/support/backoff.c',
'src/core/lib/support/cmdline.c',
diff --git a/grpc.gemspec b/grpc.gemspec
index 1ca2446e65..95aba00fd7 100755
--- a/grpc.gemspec
+++ b/grpc.gemspec
@@ -97,6 +97,7 @@ Gem::Specification.new do |s|
s.files += %w( src/core/lib/profiling/basic_timers.c )
s.files += %w( src/core/lib/profiling/stap_timers.c )
s.files += %w( src/core/lib/support/alloc.c )
+ s.files += %w( src/core/lib/support/atm.c )
s.files += %w( src/core/lib/support/avl.c )
s.files += %w( src/core/lib/support/backoff.c )
s.files += %w( src/core/lib/support/cmdline.c )
diff --git a/include/grpc/impl/codegen/atm.h b/include/grpc/impl/codegen/atm.h
index ae00fb0f16..4bd572d6d1 100644
--- a/include/grpc/impl/codegen/atm.h
+++ b/include/grpc/impl/codegen/atm.h
@@ -92,4 +92,9 @@
#error could not determine platform for atm
#endif
+/** Adds \a delta to \a *value, clamping the result to the range specified
+ by \a min and \a max. Returns the new value. */
+gpr_atm gpr_atm_no_barrier_clamped_add(gpr_atm *value, gpr_atm delta,
+ gpr_atm min, gpr_atm max);
+
#endif /* GRPC_IMPL_CODEGEN_ATM_H */
diff --git a/package.xml b/package.xml
index e29f462d33..83ad2d2129 100644
--- a/package.xml
+++ b/package.xml
@@ -106,6 +106,7 @@
<file baseinstalldir="/" name="src/core/lib/profiling/basic_timers.c" role="src" />
<file baseinstalldir="/" name="src/core/lib/profiling/stap_timers.c" role="src" />
<file baseinstalldir="/" name="src/core/lib/support/alloc.c" role="src" />
+ <file baseinstalldir="/" name="src/core/lib/support/atm.c" role="src" />
<file baseinstalldir="/" name="src/core/lib/support/avl.c" role="src" />
<file baseinstalldir="/" name="src/core/lib/support/backoff.c" role="src" />
<file baseinstalldir="/" name="src/core/lib/support/cmdline.c" role="src" />
diff --git a/src/core/ext/client_channel/retry_throttle.c b/src/core/ext/client_channel/retry_throttle.c
index 7b813c33df..8926c3d782 100644
--- a/src/core/ext/client_channel/retry_throttle.c
+++ b/src/core/ext/client_channel/retry_throttle.c
@@ -73,20 +73,9 @@ bool grpc_server_retry_throttle_data_record_failure(
// First, check if we are stale and need to be replaced.
get_replacement_throttle_data_if_needed(&throttle_data);
// We decrement milli_tokens by 1000 (1 token) for each failure.
- const int delta = -1000;
- const int old_value = (int)gpr_atm_full_fetch_add(
- &throttle_data->milli_tokens, (gpr_atm)delta);
- // If the above change takes us below 0, then re-add the excess. Note
- // that between these two atomic operations, the value will be
- // artificially low by as much as 1000, but this window should be
- // brief.
- int new_value = old_value - 1000;
- if (new_value < 0) {
- const int excess_value = new_value - (old_value < 0 ? old_value : 0);
- gpr_atm_full_fetch_add(&throttle_data->milli_tokens,
- (gpr_atm)-excess_value);
- new_value = 0;
- }
+ const int new_value = (int)gpr_atm_no_barrier_clamped_add(
+ &throttle_data->milli_tokens, (gpr_atm)-1000, (gpr_atm)0,
+ (gpr_atm)throttle_data->max_milli_tokens);
// Retries are allowed as long as the new value is above the threshold
// (max_milli_tokens / 2).
return new_value > throttle_data->max_milli_tokens / 2;
@@ -97,22 +86,9 @@ void grpc_server_retry_throttle_data_record_success(
// First, check if we are stale and need to be replaced.
get_replacement_throttle_data_if_needed(&throttle_data);
// We increment milli_tokens by milli_token_ratio for each success.
- const int delta = throttle_data->milli_token_ratio;
- const int old_value = (int)gpr_atm_full_fetch_add(
- &throttle_data->milli_tokens, (gpr_atm)delta);
- // If the above change takes us over max_milli_tokens, then subtract
- // the excess. Note that between these two atomic operations, the
- // value will be artificially high by as much as milli_token_ratio,
- // but this window should be brief.
- const int new_value = old_value + throttle_data->milli_token_ratio;
- if (new_value > throttle_data->max_milli_tokens) {
- const int excess_value =
- new_value - (old_value > throttle_data->max_milli_tokens
- ? old_value
- : throttle_data->max_milli_tokens);
- gpr_atm_full_fetch_add(&throttle_data->milli_tokens,
- (gpr_atm)-excess_value);
- }
+ gpr_atm_no_barrier_clamped_add(
+ &throttle_data->milli_tokens, (gpr_atm)throttle_data->milli_token_ratio,
+ (gpr_atm)0, (gpr_atm)throttle_data->max_milli_tokens);
}
grpc_server_retry_throttle_data* grpc_server_retry_throttle_data_ref(
diff --git a/src/core/lib/support/atm.c b/src/core/lib/support/atm.c
new file mode 100644
index 0000000000..06e8432caf
--- /dev/null
+++ b/src/core/lib/support/atm.c
@@ -0,0 +1,47 @@
+/*
+ *
+ * Copyright 2017, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ * * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ * * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include <grpc/support/atm.h>
+#include <grpc/support/useful.h>
+
+gpr_atm gpr_atm_no_barrier_clamped_add(gpr_atm *value, gpr_atm delta,
+ gpr_atm min, gpr_atm max) {
+ gpr_atm current;
+ gpr_atm new;
+ do {
+ current = gpr_atm_no_barrier_load(value);
+ new = GPR_CLAMP(current + delta, min, max);
+ if (new == current) break;
+ } while (!gpr_atm_no_barrier_cas(value, current, new));
+ return new;
+}
diff --git a/src/python/grpcio/grpc_core_dependencies.py b/src/python/grpcio/grpc_core_dependencies.py
index 94d6e46cae..da0dba7dfe 100644
--- a/src/python/grpcio/grpc_core_dependencies.py
+++ b/src/python/grpcio/grpc_core_dependencies.py
@@ -33,6 +33,7 @@ CORE_SOURCE_FILES = [
'src/core/lib/profiling/basic_timers.c',
'src/core/lib/profiling/stap_timers.c',
'src/core/lib/support/alloc.c',
+ 'src/core/lib/support/atm.c',
'src/core/lib/support/avl.c',
'src/core/lib/support/backoff.c',
'src/core/lib/support/cmdline.c',
diff --git a/tools/doxygen/Doxyfile.core.internal b/tools/doxygen/Doxyfile.core.internal
index fbe1f7f78e..7147d152ef 100644
--- a/tools/doxygen/Doxyfile.core.internal
+++ b/tools/doxygen/Doxyfile.core.internal
@@ -1230,6 +1230,7 @@ src/core/lib/slice/slice_internal.h \
src/core/lib/slice/slice_string_helpers.c \
src/core/lib/slice/slice_string_helpers.h \
src/core/lib/support/alloc.c \
+src/core/lib/support/atm.c \
src/core/lib/support/avl.c \
src/core/lib/support/backoff.c \
src/core/lib/support/backoff.h \
diff --git a/tools/run_tests/generated/sources_and_headers.json b/tools/run_tests/generated/sources_and_headers.json
index b2f9078c05..7a6295cf72 100644
--- a/tools/run_tests/generated/sources_and_headers.json
+++ b/tools/run_tests/generated/sources_and_headers.json
@@ -7311,6 +7311,7 @@
"src/core/lib/profiling/stap_timers.c",
"src/core/lib/profiling/timers.h",
"src/core/lib/support/alloc.c",
+ "src/core/lib/support/atm.c",
"src/core/lib/support/avl.c",
"src/core/lib/support/backoff.c",
"src/core/lib/support/backoff.h",
diff --git a/vsprojects/vcxproj/gpr/gpr.vcxproj b/vsprojects/vcxproj/gpr/gpr.vcxproj
index 44c21ddeb3..67ac3b98c5 100644
--- a/vsprojects/vcxproj/gpr/gpr.vcxproj
+++ b/vsprojects/vcxproj/gpr/gpr.vcxproj
@@ -208,6 +208,8 @@
</ClCompile>
<ClCompile Include="$(SolutionDir)\..\src\core\lib\support\alloc.c">
</ClCompile>
+ <ClCompile Include="$(SolutionDir)\..\src\core\lib\support\atm.c">
+ </ClCompile>
<ClCompile Include="$(SolutionDir)\..\src\core\lib\support\avl.c">
</ClCompile>
<ClCompile Include="$(SolutionDir)\..\src\core\lib\support\backoff.c">
diff --git a/vsprojects/vcxproj/gpr/gpr.vcxproj.filters b/vsprojects/vcxproj/gpr/gpr.vcxproj.filters
index a5924a624a..c49c87ed60 100644
--- a/vsprojects/vcxproj/gpr/gpr.vcxproj.filters
+++ b/vsprojects/vcxproj/gpr/gpr.vcxproj.filters
@@ -10,6 +10,9 @@
<ClCompile Include="$(SolutionDir)\..\src\core\lib\support\alloc.c">
<Filter>src\core\lib\support</Filter>
</ClCompile>
+ <ClCompile Include="$(SolutionDir)\..\src\core\lib\support\atm.c">
+ <Filter>src\core\lib\support</Filter>
+ </ClCompile>
<ClCompile Include="$(SolutionDir)\..\src\core\lib\support\avl.c">
<Filter>src\core\lib\support</Filter>
</ClCompile>
--
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