sched_ext: Simplify task state handling

Task states (NONE, INIT, READY, ENABLED) were defined in a separate enum with
unshifted values and then shifted when stored in scx_entity.flags. Simplify by
defining them as pre-shifted values directly in scx_ent_flags and removing the
separate scx_task_state enum. This removes the need for shifting when
reading/writing state values.

scx_get_task_state() now returns the masked flags value directly.
scx_set_task_state() accepts the pre-shifted state value. scx_dump_task()
shifts down for display to maintain readable output.

No functional changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>

diff --git a/include/linux/sched/ext.h b/include/linux/sched/ext.h
index e77504faa0bcbbe90239285bbaecaf0e7d0afbec..e822b374b17f822a9bfcf146c90146f72a98449d 100644 (file)
--- a/include/linux/sched/ext.h
+++ b/include/linux/sched/ext.h
@@ -93,7 +93,7 @@ struct scx_dispatch_q {
        struct rcu_head         rcu;
 };
 
-/* scx_entity.flags */
+/* sched_ext_entity.flags */
 enum scx_ent_flags {
        SCX_TASK_QUEUED         = 1 << 0, /* on ext runqueue */
        SCX_TASK_IN_CUSTODY     = 1 << 1, /* in custody, needs ops.dequeue() when leaving */
@@ -101,21 +101,25 @@ enum scx_ent_flags {
        SCX_TASK_DEQD_FOR_SLEEP = 1 << 3, /* last dequeue was for SLEEP */
        SCX_TASK_SUB_INIT       = 1 << 4, /* task being initialized for a sub sched */
 
-       SCX_TASK_STATE_SHIFT    = 8,      /* bit 8 and 9 are used to carry scx_task_state */
+       /*
+        * Bits 8 and 9 are used to carry task state:
+        *
+        * NONE         ops.init_task() not called yet
+        * INIT         ops.init_task() succeeded, but task can be cancelled
+        * READY        fully initialized, but not in sched_ext
+        * ENABLED      fully initialized and in sched_ext
+        */
+       SCX_TASK_STATE_SHIFT    = 8,      /* bits 8 and 9 are used to carry task state */
        SCX_TASK_STATE_BITS     = 2,
        SCX_TASK_STATE_MASK     = ((1 << SCX_TASK_STATE_BITS) - 1) << SCX_TASK_STATE_SHIFT,
 
-       SCX_TASK_CURSOR         = 1 << 31, /* iteration cursor, not a task */
-};
-
-/* scx_entity.flags & SCX_TASK_STATE_MASK */
-enum scx_task_state {
-       SCX_TASK_NONE,          /* ops.init_task() not called yet */
-       SCX_TASK_INIT,          /* ops.init_task() succeeded, but task can be cancelled */
-       SCX_TASK_READY,         /* fully initialized, but not in sched_ext */
-       SCX_TASK_ENABLED,       /* fully initialized and in sched_ext */
+       SCX_TASK_NONE           = 0 << SCX_TASK_STATE_SHIFT,
+       SCX_TASK_INIT           = 1 << SCX_TASK_STATE_SHIFT,
+       SCX_TASK_READY          = 2 << SCX_TASK_STATE_SHIFT,
+       SCX_TASK_ENABLED        = 3 << SCX_TASK_STATE_SHIFT,
 
-       SCX_TASK_NR_STATES,
+       /* iteration cursor, not a task */
+       SCX_TASK_CURSOR         = 1 << 31,
 };
 
 /* scx_entity.dsq_flags */

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index ee756f1a70e1de851ead8fedf8278ca6d44445cc..f55e1603fc8cea147ae14c655e88a0aead383eb9 100644 (file)
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -3284,18 +3284,16 @@ static struct cgroup *tg_cgrp(struct task_group *tg)
 
 #endif /* CONFIG_EXT_GROUP_SCHED */
 
-static enum scx_task_state scx_get_task_state(const struct task_struct *p)
+static u32 scx_get_task_state(const struct task_struct *p)
 {
-       return (p->scx.flags & SCX_TASK_STATE_MASK) >> SCX_TASK_STATE_SHIFT;
+       return p->scx.flags & SCX_TASK_STATE_MASK;
 }
 
-static void scx_set_task_state(struct task_struct *p, enum scx_task_state state)
+static void scx_set_task_state(struct task_struct *p, u32 state)
 {
-       enum scx_task_state prev_state = scx_get_task_state(p);
+       u32 prev_state = scx_get_task_state(p);
        bool warn = false;
 
-       BUILD_BUG_ON(SCX_TASK_NR_STATES > (1 << SCX_TASK_STATE_BITS));
-
        switch (state) {
        case SCX_TASK_NONE:
                break;
@@ -3313,11 +3311,11 @@ static void scx_set_task_state(struct task_struct *p, enum scx_task_state state)
                return;
        }
 
-       WARN_ONCE(warn, "sched_ext: Invalid task state transition %d -> %d for %s[%d]",
+       WARN_ONCE(warn, "sched_ext: Invalid task state transition 0x%x -> 0x%x for %s[%d]",
                  prev_state, state, p->comm, p->pid);
 
        p->scx.flags &= ~SCX_TASK_STATE_MASK;
-       p->scx.flags |= state << SCX_TASK_STATE_SHIFT;
+       p->scx.flags |= state;
 }
 
 static int __scx_init_task(struct scx_sched *sch, struct task_struct *p, bool fork)
@@ -5794,7 +5792,8 @@ static void scx_dump_task(struct scx_sched *sch,
                  own_marker, sch_id_buf,
                  jiffies_delta_msecs(p->scx.runnable_at, dctx->at_jiffies));
        dump_line(s, "      scx_state/flags=%u/0x%x dsq_flags=0x%x ops_state/qseq=%lu/%lu",
-                 scx_get_task_state(p), p->scx.flags & ~SCX_TASK_STATE_MASK,
+                 scx_get_task_state(p) >> SCX_TASK_STATE_SHIFT,
+                 p->scx.flags & ~SCX_TASK_STATE_MASK,
                  p->scx.dsq_flags, ops_state & SCX_OPSS_STATE_MASK,
                  ops_state >> SCX_OPSS_QSEQ_SHIFT);
        dump_line(s, "      sticky/holding_cpu=%d/%d dsq_id=%s",
@@ -6558,7 +6557,7 @@ static struct scx_sched *find_parent_sched(struct cgroup *cgrp)
 
 static bool assert_task_ready_or_enabled(struct task_struct *p)
 {
-       enum scx_task_state state = scx_get_task_state(p);
+       u32 state = scx_get_task_state(p);
 
        switch (state) {
        case SCX_TASK_READY: