libbinder: setMinSchedulerPolicy
This function on BBinder allows the minimum scheduling priority for
incoming binder transactions to be set by the binder driver. This
functionality was originally developed for libhwbinder and ported here.
The main difference from libhwbider is that invalid priority sets cause
an abort, whereas for libhwbinder, an error is returned. Unfortunately,
that error is frequently ignored, and since this reflects static
configuration, abort is considered a benefit.
Bug: 149933095
Test: binderLibTest
Change-Id: Ie93aebb09f4142cd66d841ca8b3ca39d1e0bb75e
diff --git a/libs/binder/Binder.cpp b/libs/binder/Binder.cpp
index e0fb543..6ca3b16 100644
--- a/libs/binder/Binder.cpp
+++ b/libs/binder/Binder.cpp
@@ -24,6 +24,7 @@
#include <binder/IShellCallback.h>
#include <binder/Parcel.h>
+#include <linux/sched.h>
#include <stdio.h>
namespace android {
@@ -133,6 +134,8 @@
// unlocked objects
bool mRequestingSid = false;
sp<IBinder> mExtension;
+ int mPolicy = SCHED_NORMAL;
+ int mPriority = 0;
// for below objects
Mutex mLock;
@@ -279,6 +282,47 @@
return e->mExtension;
}
+void BBinder::setMinSchedulerPolicy(int policy, int priority) {
+ switch (policy) {
+ case SCHED_NORMAL:
+ LOG_ALWAYS_FATAL_IF(priority < -20 || priority > 19, "Invalid priority for SCHED_NORMAL: %d", priority);
+ break;
+ case SCHED_RR:
+ case SCHED_FIFO:
+ LOG_ALWAYS_FATAL_IF(priority < 1 || priority > 99, "Invalid priority for sched %d: %d", policy, priority);
+ break;
+ default:
+ LOG_ALWAYS_FATAL("Unrecognized scheduling policy: %d", policy);
+ }
+
+ Extras* e = mExtras.load(std::memory_order_acquire);
+
+ if (e == nullptr) {
+ // Avoid allocations if called with default.
+ if (policy == SCHED_NORMAL && priority == 0) {
+ return;
+ }
+
+ e = getOrCreateExtras();
+ if (!e) return; // out of memory
+ }
+
+ e->mPolicy = policy;
+ e->mPriority = priority;
+}
+
+int BBinder::getMinSchedulerPolicy() {
+ Extras* e = mExtras.load(std::memory_order_acquire);
+ if (e == nullptr) return SCHED_NORMAL;
+ return e->mPolicy;
+}
+
+int BBinder::getMinSchedulerPriority() {
+ Extras* e = mExtras.load(std::memory_order_acquire);
+ if (e == nullptr) return 0;
+ return e->mPriority;
+}
+
pid_t BBinder::getDebugPid() {
return getpid();
}
diff --git a/libs/binder/Parcel.cpp b/libs/binder/Parcel.cpp
index 660b96a..c7cb495 100644
--- a/libs/binder/Parcel.cpp
+++ b/libs/binder/Parcel.cpp
@@ -20,6 +20,7 @@
#include <errno.h>
#include <fcntl.h>
#include <inttypes.h>
+#include <linux/sched.h>
#include <pthread.h>
#include <stdint.h>
#include <stdio.h>
@@ -188,16 +189,18 @@
return OK;
}
+static constexpr inline int schedPolicyMask(int policy, int priority) {
+ return (priority & FLAT_BINDER_FLAG_PRIORITY_MASK) | ((policy & 3) << FLAT_BINDER_FLAG_SCHED_POLICY_SHIFT);
+}
+
status_t Parcel::flattenBinder(const sp<IBinder>& binder)
{
flat_binder_object obj;
+ obj.flags = FLAT_BINDER_FLAG_ACCEPTS_FDS;
- if (IPCThreadState::self()->backgroundSchedulingDisabled()) {
- /* minimum priority for all nodes is nice 0 */
- obj.flags = FLAT_BINDER_FLAG_ACCEPTS_FDS;
- } else {
- /* minimum priority for all nodes is MAX_NICE(19) */
- obj.flags = 0x13 | FLAT_BINDER_FLAG_ACCEPTS_FDS;
+ int schedBits = 0;
+ if (!IPCThreadState::self()->backgroundSchedulingDisabled()) {
+ schedBits = schedPolicyMask(SCHED_NORMAL, 19);
}
if (binder != nullptr) {
@@ -213,6 +216,13 @@
obj.handle = handle;
obj.cookie = 0;
} else {
+ int policy = local->getMinSchedulerPolicy();
+ int priority = local->getMinSchedulerPriority();
+
+ if (policy != 0 || priority != 0) {
+ // override value, since it is set explicitly
+ schedBits = schedPolicyMask(policy, priority);
+ }
if (local->isRequestingSid()) {
obj.flags |= FLAT_BINDER_FLAG_TXN_SECURITY_CTX;
}
@@ -226,6 +236,8 @@
obj.cookie = 0;
}
+ obj.flags |= schedBits;
+
return finishFlattenBinder(binder, obj);
}
diff --git a/libs/binder/include/binder/Binder.h b/libs/binder/include/binder/Binder.h
index 74e52db..f3fea16 100644
--- a/libs/binder/include/binder/Binder.h
+++ b/libs/binder/include/binder/Binder.h
@@ -72,6 +72,22 @@
// This must be called before the object is sent to another process. Not thread safe.
void setExtension(const sp<IBinder>& extension);
+ // This must be called before the object is sent to another process. Not thread safe.
+ //
+ // This function will abort if improper parameters are set. This is like
+ // sched_setscheduler. However, it sets the minimum scheduling policy
+ // only for the duration that this specific binder object is handling the
+ // call in a threadpool. By default, this API is set to SCHED_NORMAL/0. In
+ // this case, the scheduling priority will not actually be modified from
+ // binder defaults. See also IPCThreadState::disableBackgroundScheduling.
+ //
+ // Appropriate values are:
+ // SCHED_NORMAL: -20 <= priority <= 19
+ // SCHED_RR/SCHED_FIFO: 1 <= priority <= 99
+ void setMinSchedulerPolicy(int policy, int priority);
+ int getMinSchedulerPolicy();
+ int getMinSchedulerPriority();
+
pid_t getDebugPid();
protected:
diff --git a/libs/binder/tests/binderLibTest.cpp b/libs/binder/tests/binderLibTest.cpp
index 8cb06e1..f8ee32c 100644
--- a/libs/binder/tests/binderLibTest.cpp
+++ b/libs/binder/tests/binderLibTest.cpp
@@ -48,6 +48,9 @@
static char *binderserversuffix;
static char binderserverarg[] = "--binderserver";
+static constexpr int kSchedPolicy = SCHED_RR;
+static constexpr int kSchedPriority = 7;
+
static String16 binderLibTestServiceName = String16("test.binderLib");
enum BinderLibTestTranscationCode {
@@ -73,6 +76,7 @@
BINDER_LIB_TEST_GET_PTR_SIZE_TRANSACTION,
BINDER_LIB_TEST_CREATE_BINDER_TRANSACTION,
BINDER_LIB_TEST_GET_WORK_SOURCE_TRANSACTION,
+ BINDER_LIB_TEST_GET_SCHEDULING_POLICY,
BINDER_LIB_TEST_ECHO_VECTOR,
};
@@ -1012,6 +1016,22 @@
EXPECT_EQ(NO_ERROR, ret2);
}
+TEST_F(BinderLibTest, SchedPolicySet) {
+ sp<IBinder> server = addServer();
+ ASSERT_TRUE(server != nullptr);
+
+ Parcel data, reply;
+ status_t ret = server->transact(BINDER_LIB_TEST_GET_SCHEDULING_POLICY, data, &reply);
+ EXPECT_EQ(NO_ERROR, ret);
+
+ int policy = reply.readInt32();
+ int priority = reply.readInt32();
+
+ EXPECT_EQ(kSchedPolicy, policy & (~SCHED_RESET_ON_FORK));
+ EXPECT_EQ(kSchedPriority, priority);
+}
+
+
TEST_F(BinderLibTest, VectorSent) {
Parcel data, reply;
sp<IBinder> server = addServer();
@@ -1301,6 +1321,16 @@
reply->writeInt32(IPCThreadState::self()->getCallingWorkSourceUid());
return NO_ERROR;
}
+ case BINDER_LIB_TEST_GET_SCHEDULING_POLICY: {
+ int policy = 0;
+ sched_param param;
+ if (0 != pthread_getschedparam(pthread_self(), &policy, ¶m)) {
+ return UNKNOWN_ERROR;
+ }
+ reply->writeInt32(policy);
+ reply->writeInt32(param.sched_priority);
+ return NO_ERROR;
+ }
case BINDER_LIB_TEST_ECHO_VECTOR: {
std::vector<uint64_t> vector;
auto err = data.readUint64Vector(&vector);
@@ -1334,6 +1364,8 @@
{
sp<BinderLibTestService> testService = new BinderLibTestService(index);
+ testService->setMinSchedulerPolicy(kSchedPolicy, kSchedPriority);
+
/*
* Normally would also contain functionality as well, but we are only
* testing the extension mechanism.