locking/ww_mutex: Support Clang's context analysis

Add support for Clang's context analysis for ww_mutex.

The programming model for ww_mutex is subtly more complex than other
locking primitives when using ww_acquire_ctx. Encoding the respective
pre-conditions for ww_mutex lock/unlock based on ww_acquire_ctx state
using Clang's context analysis makes incorrect use of the API harder.

Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20251219154418.3592607-21-elver@google.com

1 files changed, 69 insertions, 0 deletions

diff --git a/lib/test_context-analysis.c b/lib/test_context-analysis.c
index 003e64cac540..2dc404456497 100644
--- a/lib/test_context-analysis.c
+++ b/lib/test_context-analysis.c
@@ -14,6 +14,7 @@
 #include <linux/seqlock.h>
 #include <linux/spinlock.h>
 #include <linux/srcu.h>
+#include <linux/ww_mutex.h>
 
 /*
  * Test that helper macros work as expected.
@@ -531,3 +532,71 @@ static void __used test_local_trylock(void)
 		local_unlock(&test_local_trylock_data.lock);
 	}
 }
+
+static DEFINE_WD_CLASS(ww_class);
+
+struct test_ww_mutex_data {
+	struct ww_mutex mtx;
+	int counter __guarded_by(&mtx);
+};
+
+static void __used test_ww_mutex_init(struct test_ww_mutex_data *d)
+{
+	ww_mutex_init(&d->mtx, &ww_class);
+	d->counter = 0;
+}
+
+static void __used test_ww_mutex_lock_noctx(struct test_ww_mutex_data *d)
+{
+	if (!ww_mutex_lock(&d->mtx, NULL)) {
+		d->counter++;
+		ww_mutex_unlock(&d->mtx);
+	}
+
+	if (!ww_mutex_lock_interruptible(&d->mtx, NULL)) {
+		d->counter++;
+		ww_mutex_unlock(&d->mtx);
+	}
+
+	if (ww_mutex_trylock(&d->mtx, NULL)) {
+		d->counter++;
+		ww_mutex_unlock(&d->mtx);
+	}
+
+	ww_mutex_lock_slow(&d->mtx, NULL);
+	d->counter++;
+	ww_mutex_unlock(&d->mtx);
+
+	ww_mutex_destroy(&d->mtx);
+}
+
+static void __used test_ww_mutex_lock_ctx(struct test_ww_mutex_data *d)
+{
+	struct ww_acquire_ctx ctx;
+
+	ww_acquire_init(&ctx, &ww_class);
+
+	if (!ww_mutex_lock(&d->mtx, &ctx)) {
+		d->counter++;
+		ww_mutex_unlock(&d->mtx);
+	}
+
+	if (!ww_mutex_lock_interruptible(&d->mtx, &ctx)) {
+		d->counter++;
+		ww_mutex_unlock(&d->mtx);
+	}
+
+	if (ww_mutex_trylock(&d->mtx, &ctx)) {
+		d->counter++;
+		ww_mutex_unlock(&d->mtx);
+	}
+
+	ww_mutex_lock_slow(&d->mtx, &ctx);
+	d->counter++;
+	ww_mutex_unlock(&d->mtx);
+
+	ww_acquire_done(&ctx);
+	ww_acquire_fini(&ctx);
+
+	ww_mutex_destroy(&d->mtx);
+}