[PATCH 03/13] ANDROID: binder: add support for RT prio inheritance.

Martijn Coenen
2017-08-25T09:38:31Z

Adds support for SCHED_BATCH/SCHED_FIFO/SCHED_RR
priority inheritance.

Signed-off-by: Martijn Coenen <maco@android.com>
---
drivers/android/binder.c | 164 ++++++++++++++++++++++++++++++++++++++---------
1 file changed, 135 insertions(+), 29 deletions(-)

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 2f27bce31baf..bb61116d1c0c 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -77,6 +77,7 @@
#endif

#include <uapi/linux/android/binder.h>
+#include <uapi/linux/sched/types.h>
#include "binder_alloc.h"
#include "binder_trace.h"

@@ -463,6 +464,22 @@ enum binder_deferred_state {
BINDER_DEFERRED_RELEASE = 0x04,
};

+/**
+ * struct binder_priority - scheduler policy and priority
+ * @sched_policy scheduler policy
+ * @prio [100..139] for SCHED_NORMAL, [0..99] for FIFO/RT
+ *
+ * The binder driver supports inheriting the following scheduler policies:
+ * SCHED_NORMAL
+ * SCHED_BATCH
+ * SCHED_FIFO
+ * SCHED_RR
+ */
+struct binder_priority {
+ unsigned int sched_policy;
+ int prio;
+};
+
/**
* struct binder_proc - binder process bookkeeping
* @proc_node: element for binder_procs list
@@ -542,7 +559,7 @@ struct binder_proc {
int requested_threads;
int requested_threads_started;
int tmp_ref;
- long default_priority;
+ struct binder_priority default_priority;
struct dentry *debugfs_entry;
struct binder_alloc alloc;
struct binder_context *context;
@@ -624,8 +641,8 @@ struct binder_transaction {
struct binder_buffer *buffer;
unsigned int code;
unsigned int flags;
- long priority;
- long saved_priority;
+ struct binder_priority priority;
+ struct binder_priority saved_priority;
kuid_t sender_euid;
/**
* @lock: protects @from, @to_proc, and @to_thread
@@ -1051,22 +1068,93 @@ static void binder_wakeup_proc_ilocked(struct binder_proc *proc)
binder_wakeup_thread_ilocked(proc, thread, /* sync = */false);
}

-static void binder_set_nice(long nice)
+static bool is_rt_policy(int policy)
+{
+ return policy == SCHED_FIFO || policy == SCHED_RR;
+}
+
+static bool is_fair_policy(int policy)
+{
+ return policy == SCHED_NORMAL || policy == SCHED_BATCH;
+}
+
+static bool binder_supported_policy(int policy)
+{
+ return is_fair_policy(policy) || is_rt_policy(policy);
+}
+
+static int to_userspace_prio(int policy, int kernel_priority)
+{
+ if (is_fair_policy(policy))
+ return PRIO_TO_NICE(kernel_priority);
+ else
+ return MAX_USER_RT_PRIO - 1 - kernel_priority;
+}
+
+static int to_kernel_prio(int policy, int user_priority)
+{
+ if (is_fair_policy(policy))
+ return NICE_TO_PRIO(user_priority);
+ else
+ return MAX_USER_RT_PRIO - 1 - user_priority;
+}
+
+static void binder_set_priority(struct task_struct *task,
+ struct binder_priority desired)
{
- long min_nice;
+ int priority; /* user-space prio value */
+ bool has_cap_nice;
+ unsigned int policy = desired.sched_policy;

- if (can_nice(current, nice)) {
- set_user_nice(current, nice);
+ if (task->policy == policy && task->normal_prio == desired.prio)
return;
+
+ has_cap_nice = has_capability_noaudit(task, CAP_SYS_NICE);
+
+ priority = to_userspace_prio(policy, desired.prio);
+
+ if (is_rt_policy(policy) && !has_cap_nice) {
+ long max_rtprio = task_rlimit(task, RLIMIT_RTPRIO);
+
+ if (max_rtprio == 0) {
+ policy = SCHED_NORMAL;
+ priority = MIN_NICE;
+ } else if (priority > max_rtprio) {
+ priority = max_rtprio;
+ }
}
- min_nice = rlimit_to_nice(rlimit(RLIMIT_NICE));
- binder_debug(BINDER_DEBUG_PRIORITY_CAP,
- "%d: nice value %ld not allowed use %ld instead\n",
- current->pid, nice, min_nice);
- set_user_nice(current, min_nice);
- if (min_nice <= MAX_NICE)
- return;
- binder_user_error("%d RLIMIT_NICE not set\n", current->pid);
+
+ if (is_fair_policy(policy) && !has_cap_nice) {
+ long min_nice = rlimit_to_nice(task_rlimit(task, RLIMIT_NICE));
+
+ if (min_nice > MAX_NICE) {
+ binder_user_error("%d RLIMIT_NICE not set\n",
+ task->pid);
+ return;
+ } else if (priority < min_nice) {
+ priority = min_nice;
+ }
+ }
+
+ if (policy != desired.sched_policy ||
+ to_kernel_prio(policy, priority) != desired.prio)
+ binder_debug(BINDER_DEBUG_PRIORITY_CAP,
+ "%d: priority %d not allowed, using %d instead\n",
+ task->pid, desired.prio,
+ to_kernel_prio(policy, priority));
+
+ /* Set the actual priority */
+ if (task->policy != policy || is_rt_policy(policy)) {
+ struct sched_param params;
+
+ params.sched_priority = is_rt_policy(policy) ? priority : 0;
+
+ sched_setscheduler_nocheck(task,
+ policy | SCHED_RESET_ON_FORK,
+ &params);
+ }
+ if (is_fair_policy(policy))
+ set_user_nice(task, priority);
}

static struct binder_node *binder_get_node_ilocked(struct binder_proc *proc,
@@ -1150,7 +1238,8 @@ static struct binder_node *binder_init_node_ilocked(
node->ptr = ptr;
node->cookie = cookie;
node->work.type = BINDER_WORK_NODE;
- node->min_priority = flags & FLAT_BINDER_FLAG_PRIORITY_MASK;
+ node->min_priority = NICE_TO_PRIO(
+ flags & FLAT_BINDER_FLAG_PRIORITY_MASK);
node->accept_fds = !!(flags & FLAT_BINDER_FLAG_ACCEPTS_FDS);
spin_lock_init(&node->lock);
INIT_LIST_HEAD(&node->work.entry);
@@ -2646,7 +2735,7 @@ static void binder_transaction(struct binder_proc *proc,
}
thread->transaction_stack = in_reply_to->to_parent;
binder_inner_proc_unlock(proc);
- binder_set_nice(in_reply_to->saved_priority);
+ binder_set_priority(current, in_reply_to->saved_priority);
target_thread = binder_get_txn_from_and_acq_inner(in_reply_to);
if (target_thread == NULL) {
return_error = BR_DEAD_REPLY;
@@ -2819,7 +2908,15 @@ static void binder_transaction(struct binder_proc *proc,
t->to_thread = target_thread;
t->code = tr->code;
t->flags = tr->flags;
- t->priority = task_nice(current);
+ if (!(t->flags & TF_ONE_WAY) &&
+ binder_supported_policy(current->policy)) {
+ /* Inherit supported policies for synchronous transactions */
+ t->priority.sched_policy = current->policy;
+ t->priority.prio = current->normal_prio;
+ } else {
+ /* Otherwise, fall back to the default priority */
+ t->priority = target_proc->default_priority;
+ }

trace_binder_transaction(reply, t, target_node);

@@ -3735,7 +3832,7 @@ static int binder_thread_read(struct binder_proc *proc,
wait_event_interruptible(binder_user_error_wait,
binder_stop_on_user_error < 2);
}
- binder_set_nice(proc->default_priority);
+ binder_set_priority(current, proc->default_priority);
}

if (non_block) {
@@ -3947,16 +4044,17 @@ static int binder_thread_read(struct binder_proc *proc,
BUG_ON(t->buffer == NULL);
if (t->buffer->target_node) {
struct binder_node *target_node = t->buffer->target_node;
+ struct binder_priority prio = t->priority;

tr.target.ptr = target_node->ptr;
tr.cookie = target_node->cookie;
- t->saved_priority = task_nice(current);
- if (t->priority < target_node->min_priority &&
- !(t->flags & TF_ONE_WAY))
- binder_set_nice(t->priority);
- else if (!(t->flags & TF_ONE_WAY) ||
- t->saved_priority > target_node->min_priority)
- binder_set_nice(target_node->min_priority);
+ t->saved_priority.sched_policy = current->policy;
+ t->saved_priority.prio = current->normal_prio;
+ if (target_node->min_priority < t->priority.prio) {
+ prio.sched_policy = SCHED_NORMAL;
+ prio.prio = target_node->min_priority;
+ }
+ binder_set_priority(current, prio);
cmd = BR_TRANSACTION;
} else {
tr.target.ptr = 0;
@@ -4562,7 +4660,14 @@ static int binder_open(struct inode *nodp, struct file *filp)
get_task_struct(current->group_leader);
proc->tsk = current->group_leader;
INIT_LIST_HEAD(&proc->todo);
- proc->default_priority = task_nice(current);
+ if (binder_supported_policy(current->policy)) {
+ proc->default_priority.sched_policy = current->policy;
+ proc->default_priority.prio = current->normal_prio;
+ } else {
+ proc->default_priority.sched_policy = SCHED_NORMAL;
+ proc->default_priority.prio = NICE_TO_PRIO(0);
+ }
+
binder_dev = container_of(filp->private_data, struct binder_device,
miscdev);
proc->context = &binder_dev->context;
@@ -4855,13 +4960,14 @@ static void print_binder_transaction_ilocked(struct seq_file *m,
spin_lock(&t->lock);
to_proc = t->to_proc;
seq_printf(m,
- "%s %d: %p from %d:%d to %d:%d code %x flags %x pri %ld r%d",
+ "%s %d: %p from %d:%d to %d:%d code %x flags %x pri %d:%d r%d",
prefix, t->debug_id, t,
t->from ? t->from->proc->pid : 0,
t->from ? t->from->pid : 0,
to_proc ? to_proc->pid : 0,
t->to_thread ? t->to_thread->pid : 0,
- t->code, t->flags, t->priority, t->need_reply);
+ t->code, t->flags, t->priority.sched_policy,
+ t->priority.prio, t->need_reply);
spin_unlock(&t->lock);

if (proc != to_proc) {
--
2.14.1.480.gb18f417b89-goog