Add BPF Workqueues support and example

- Introduced BPF workqueues to enable asynchronous work from BPF programs, allowing deferred processing, non-blocking operations, and sleepable contexts for long-running tasks. - Added README.md to document the BPF workqueues, including use cases, technical architecture, and code examples. - Created bpf_experimental.h header file to define necessary BPF workqueue functions and structures. - Implemented a simple BPF workqueue example (wq_simple) demonstrating the initialization, scheduling, and execution of work in a separate context. - Developed a userspace test (wq_simple.c) to verify the functionality of the BPF workqueue by triggering a syscall and checking the execution results.
2026-02-08 12:53:33 +08:00 · 2025-10-04 22:49:09 -07:00
parent ba1a6a472e
commit b88ab2ae0e
11 changed files with 1755 additions and 0 deletions
--- a/src/features/bpf_iters/task_stack.bpf.c
+++ b/src/features/bpf_iters/task_stack.bpf.c
@@ -0,0 +1,118 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Kernel task stack and file descriptor iterator */
+#include <vmlinux.h>
+#include <bpf/bpf_helpers.h>
+
+char _license[] SEC("license") = "GPL";
+
+#define MAX_STACK_TRACE_DEPTH   64
+unsigned long entries[MAX_STACK_TRACE_DEPTH] = {};
+#define SIZE_OF_ULONG (sizeof(unsigned long))
+
+/* Filter: only show stacks for tasks with this name (empty = show all) */
+char target_comm[16] = "";
+__u32 stacks_shown = 0;
+__u32 files_shown = 0;
+
+/* Task stack iterator */
+SEC("iter/task")
+int dump_task_stack(struct bpf_iter__task *ctx)
+{
+	struct seq_file *seq = ctx->meta->seq;
+	struct task_struct *task = ctx->task;
+	long i, retlen;
+	int match = 1;
+
+	if (task == (void *)0) {
+		/* End of iteration - print summary */
+		if (stacks_shown > 0) {
+			BPF_SEQ_PRINTF(seq, "\n=== Summary: %u task stacks shown ===\n",
+				       stacks_shown);
+		}
+		return 0;
+	}
+
+	/* Filter by task name if specified */
+	if (target_comm[0] != '\0') {
+		match = 0;
+		for (i = 0; i < 16; i++) {
+			if (task->comm[i] != target_comm[i])
+				break;
+			if (task->comm[i] == '\0') {
+				match = 1;
+				break;
+			}
+		}
+		if (!match)
+			return 0;
+	}
+
+	/* Get kernel stack trace for this task */
+	retlen = bpf_get_task_stack(task, entries,
+				    MAX_STACK_TRACE_DEPTH * SIZE_OF_ULONG, 0);
+	if (retlen < 0)
+		return 0;
+
+	stacks_shown++;
+
+	/* Print task info and stack trace */
+	BPF_SEQ_PRINTF(seq, "=== Task: %s (pid=%u, tgid=%u) ===\n",
+		       task->comm, task->pid, task->tgid);
+	BPF_SEQ_PRINTF(seq, "Stack depth: %u frames\n", retlen / SIZE_OF_ULONG);
+
+	for (i = 0; i < MAX_STACK_TRACE_DEPTH; i++) {
+		if (retlen > i * SIZE_OF_ULONG)
+			BPF_SEQ_PRINTF(seq, "  [%2ld] %pB\n", i, (void *)entries[i]);
+	}
+	BPF_SEQ_PRINTF(seq, "\n");
+
+	return 0;
+}
+
+/* Task file descriptor iterator */
+SEC("iter/task_file")
+int dump_task_file(struct bpf_iter__task_file *ctx)
+{
+	struct seq_file *seq = ctx->meta->seq;
+	struct task_struct *task = ctx->task;
+	struct file *file = ctx->file;
+	__u32 fd = ctx->fd;
+	long i;
+	int match = 1;
+
+	if (task == (void *)0 || file == (void *)0) {
+		if (files_shown > 0 && ctx->meta->seq_num > 0) {
+			BPF_SEQ_PRINTF(seq, "\n=== Summary: %u file descriptors shown ===\n",
+				       files_shown);
+		}
+		return 0;
+	}
+
+	/* Filter by task name if specified */
+	if (target_comm[0] != '\0') {
+		match = 0;
+		for (i = 0; i < 16; i++) {
+			if (task->comm[i] != target_comm[i])
+				break;
+			if (task->comm[i] == '\0') {
+				match = 1;
+				break;
+			}
+		}
+		if (!match)
+			return 0;
+	}
+
+	if (ctx->meta->seq_num == 0) {
+		BPF_SEQ_PRINTF(seq, "%-16s %8s %8s %6s %s\n",
+			       "COMM", "TGID", "PID", "FD", "FILE_OPS");
+	}
+
+	files_shown++;
+
+	BPF_SEQ_PRINTF(seq, "%-16s %8d %8d %6d 0x%lx\n",
+		       task->comm, task->tgid, task->pid, fd,
+		       (long)file->f_op);
+
+	return 0;
+}