selftests/bpf: Add a test for objects stuck in free_by_rcu_ttracegrafted

Delete all elements of BPF_F_NO_PREALLOC hash map in one batch. The first
free_bulk() starts RCU tasks trace GP and the rest of the elements are
freed while it's in flight. Wait for call_rcu_ttrace_in_progress to clear
in bpf_mem_cache of every cpu and check that free_by_rcu_ttrace and
waiting_for_gp_ttrace lists are empty.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20260930095920.601738-4-alexei.starovoitov@gmail.com
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>

5 files changed, 32 insertions, 0 deletions

diff --git a/samples/rust/hostprogs/.gitignore b/samples/rust/hostprogs/.gitignore
new file mode 100644
index 000000000..a6c173da5
--- /dev/null
+++ b/samples/rust/hostprogs/.gitignore
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0
+
+single
diff --git a/samples/rust/hostprogs/Makefile b/samples/rust/hostprogs/Makefile
new file mode 100644
index 000000000..8ddcbd741
--- /dev/null
+++ b/samples/rust/hostprogs/Makefile
@@ -0,0 +1,5 @@
+# SPDX-License-Identifier: GPL-2.0
+
+hostprogs-always-y := single
+
+single-rust := y
diff --git a/samples/rust/hostprogs/a.rs b/samples/rust/hostprogs/a.rs
new file mode 100644
index 000000000..f7a4a3d0f
--- /dev/null
+++ b/samples/rust/hostprogs/a.rs
@@ -0,0 +1,7 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Rust single host program sample: module `a`.
+
+pub(crate) fn f(x: i32) {
+    println!("The number is {}.", x);
+}
diff --git a/samples/rust/hostprogs/b.rs b/samples/rust/hostprogs/b.rs
new file mode 100644
index 000000000..c16758906
--- /dev/null
+++ b/samples/rust/hostprogs/b.rs
@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Rust single host program sample: module `b`.
+
+pub(crate) const CONSTANT: i32 = 42;
diff --git a/samples/rust/hostprogs/single.rs b/samples/rust/hostprogs/single.rs
new file mode 100644
index 000000000..8c48a1193
--- /dev/null
+++ b/samples/rust/hostprogs/single.rs
@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Rust single host program sample.
+
+mod a;
+mod b;
+
+fn main() {
+    println!("Hello world!");
+
+    a::f(b::CONSTANT);
+}