[PATCH v15 15/16] barrier: timeout validity checks for smp_cond_load_relaxed_timeout()

[Ankur Arora]

Add timeout tests for smp_cond_load_relaxed_timeout().  These check
that the implementation returns early on invalid timeout values and
handles edge cases sanely.

Signed-off-by: Ankur Arora <ankur.a.arora at oracle.com>
---
 lib/tests/barrier-timeout-test.c | 86 ++++++++++++++++++++++++++++++++
 1 file changed, 86 insertions(+)

diff --git a/lib/tests/barrier-timeout-test.c b/lib/tests/barrier-timeout-test.c
index 60f121fe5472..9b16ad6f5514 100644
--- a/lib/tests/barrier-timeout-test.c
+++ b/lib/tests/barrier-timeout-test.c
@@ -19,6 +19,8 @@ MODULE_IMPORT_NS("EXPORTED_FOR_KUNIT_TESTING");
 struct clock_state {
 	s64	start_time;
 	s64	end_time;
+	s64	extra;
+	u32	niters;
 };
 
 #define TIMEOUT_MSEC	2
@@ -110,8 +112,92 @@ static void test_smp_cond_timeout(struct kunit *test)
 		KUNIT_EXPECT_GE(test, runtime, timeout_ns);
 }
 
+static s64 synthetic_clock(struct clock_state *clk)
+{
+	clk->end_time += clk->extra;
+	clk->niters++;
+
+	return clk->end_time;
+}
+
+struct smp_cond_expiry_params {
+	char	*desc;
+	u64	timeout_ns;
+	s64	clk_unit;
+	s64	miniters;
+	s64	maxiters;
+};
+
+static const struct smp_cond_expiry_params expiry_params_list[] = {
+	/* timeout_ns is invalid/out-of-range */
+	{ .clk_unit = 0, .timeout_ns = -1LL,	.miniters = -1, .maxiters = 0, .desc = "invalid (-1LL)", },
+	{ .clk_unit = 0, .timeout_ns = ~0ULL,	.miniters = -1, .maxiters = 0, .desc = "invalid (~0ULL)", },
+	{ .clk_unit = 0, .timeout_ns = S64_MAX+1ULL, .miniters = -1, .maxiters = 0, .desc = "out-of-range (S64_MAX+1)", },
+	{ .clk_unit = 0, .timeout_ns = U64_MAX,	.miniters = -1, .maxiters = 0, .desc = "out-of-range (U64_MAX)", },
+	{ .clk_unit = 0, .timeout_ns = 0,	.miniters = -1, .maxiters = 1, .desc = "degenerate (0)",    },
+
+	/* timeout_ns is valid */
+	{ .clk_unit = (0x1ULL << 28), .timeout_ns = 1,		    .miniters = 1,	      .maxiters = -1, .desc = "1",    },
+	{ .clk_unit = (0x1ULL << 28), .timeout_ns = (0x1ULL << 30), .miniters = 1 << (30-28), .maxiters = -1, .desc = "1<<30",   },
+	{ .clk_unit = (0x1ULL << 28), .timeout_ns = S32_MAX,	    .miniters = 1 << (31-28), .maxiters = -1, .desc = "S32_MAX", },
+	{ .clk_unit = (0x1ULL << 28), .timeout_ns = U32_MAX,	    .miniters = 1 << (32-28), .maxiters = -1, .desc = "U32_MAX", },
+	{ .clk_unit = (0x1ULL << 28), .timeout_ns = (0x1ULL << 33), .miniters = 1 << (33-28), .maxiters = -1, .desc = "1<<33",   },
+	{ .clk_unit = (0x1ULL << 58), .timeout_ns = S64_MAX,	    .miniters = 1 << (63-58), .maxiters = -1, .desc = "S64_MAX", },
+};
+
+static void expiry_param_to_desc(const struct smp_cond_expiry_params *p, char *desc)
+{
+	char iters[32] = "";
+
+	if (p->miniters != -1)
+		snprintf(iters, 32, ">= %llx", p->miniters);
+	else if (p->maxiters != -1)
+		snprintf(iters, 32, "%s %llx", p->maxiters == 0 ? "==" : "<=", p->maxiters);
+
+	snprintf(desc, KUNIT_PARAM_DESC_SIZE,
+		 "smp_cond_*_timeout: clock=%s,  timeout=%s, iterations %s",
+		 "synthetic", p->desc, iters);
+}
+
+static void test_smp_cond_relaxed(struct kunit *test)
+{
+	const struct smp_cond_expiry_params *p = test->param_value;
+	struct clock_state clk = {
+		.start_time = 0,
+		.end_time = 0,
+		.extra = p->clk_unit,
+		.niters = 0,
+	};
+	s64 runtime;
+
+	flag = 0;
+	smp_cond_load_relaxed_timeout(&flag,
+				      0,
+				      synthetic_clock(&clk),
+				      p->timeout_ns);
+
+	runtime = (u64)clk.end_time - (u64)clk.start_time;
+
+	/*
+	 * Check if we do the expected number of iterations.
+	 */
+	if (p->miniters != -1)
+		KUNIT_EXPECT_GE(test, clk.niters, p->miniters);
+	if (p->maxiters != -1)
+		KUNIT_EXPECT_LE(test, clk.niters, p->maxiters);
+
+	/*
+	 * maxiters == 0 means that the timeout is invalid/out-of-range.
+	 * When not, we cannot return with runtime < timeout_ns.
+	 */
+	if (p->maxiters != 0)
+		KUNIT_EXPECT_GE(test, runtime, p->timeout_ns);
+}
+
+KUNIT_ARRAY_PARAM(smp_cond_expiry_params, expiry_params_list, expiry_param_to_desc);
 static struct kunit_case barrier_timeout_test_cases[] = {
 	KUNIT_CASE_PARAM(test_smp_cond_timeout, smp_cond_update_params_gen_params),
+	KUNIT_CASE_PARAM(test_smp_cond_relaxed, smp_cond_expiry_params_gen_params),
 	{}
 };
 
-- 
2.43.7