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scx_rustland_core: avoid critical failures due by missing task context

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Prevent triggering a critical error when a local context for a task
can't be found.

Instead, handle the error gracefully (reporting a warning in debugfs) to
enhance the robustness of the schedulers based on scx_rustland_core.

Signed-off-by: Andrea Righi <andrea.righi@linux.dev>
This commit is contained in:
Andrea Righi 2024-09-04 10:03:12 +02:00
parent afc7b5404b
commit 53617042b3
1 changed files with 22 additions and 18 deletions
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40
rust/scx_rustland_core/assets/bpf/main.bpf.c
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@ -221,16 +221,17 @@ struct {
__type(value, struct task_ctx);
} task_ctx_stor SEC(".maps");
/* Return a local task context from a generic task */
struct task_ctx *lookup_task_ctx(const struct task_struct *p)
/*
* Return a local task context from a generic task or NULL if the context
* doesn't exist.
*/
struct task_ctx *try_lookup_task_ctx(const struct task_struct *p)
{
struct task_ctx *tctx;
tctx = bpf_task_storage_get(&task_ctx_stor, (struct task_struct *)p, 0, 0);
if (!tctx) {
scx_bpf_error("Failed to lookup task ctx for %s", p->comm);
return NULL;
}
struct task_ctx *tctx = bpf_task_storage_get(&task_ctx_stor,
(struct task_struct *)p, 0, 0);
if (!tctx)
dbg_msg("warning: failed to get task context for pid=%d (%s)",
p->pid, p->comm);
return tctx;
}
@ -357,7 +358,7 @@ static inline u64 task_slice(struct task_struct *p)
{
struct task_ctx *tctx;
tctx = lookup_task_ctx(p);
tctx = try_lookup_task_ctx(p);
if (!tctx || !tctx->slice_ns)
return SCX_SLICE_DFL;
return tctx->slice_ns;
@ -378,9 +379,15 @@ static void dispatch_task(struct task_struct *p, u64 dsq_id,
/*
* Update task's time slice in its context.
*/
tctx = lookup_task_ctx(p);
if (!tctx)
tctx = try_lookup_task_ctx(p);
if (!tctx) {
/*
* Bounce to the shared DSQ if we can't find a valid task
* context.
*/
scx_bpf_dispatch_vtime(p, dsq_id, SCX_SLICE_DFL, vtime, 0);
return;
}
tctx->slice_ns = slice;
/*
@ -611,16 +618,13 @@ int rs_select_cpu(struct task_cpu_arg *input)
static void
get_task_info(struct queued_task_ctx *task, const struct task_struct *p)
{
struct task_ctx *tctx;
struct task_ctx *tctx = try_lookup_task_ctx(p);
tctx = lookup_task_ctx(p);
if (!tctx)
return;
task->pid = p->pid;
task->cpumask_cnt = tctx->cpumask_cnt;
task->sum_exec_runtime = p->se.sum_exec_runtime;
task->weight = p->scx.weight;
task->cpu = scx_bpf_task_cpu(p);
task->cpumask_cnt = tctx ? tctx->cpumask_cnt : 0;
}
/*
@ -899,7 +903,7 @@ void BPF_STRUCT_OPS(rustland_set_cpumask, struct task_struct *p,
{
struct task_ctx *tctx;
tctx = lookup_task_ctx(p);
tctx = try_lookup_task_ctx(p);
if (!tctx)
return;
tctx->cpumask_cnt++;