Currently the tm-unavailable test spins for a fixed amount of time in
an attempt to ensure the FPU/VMX/VSX facilities are off. This value was
experimentally tested to be long enough.
Problems may arise if kernel heuristics were to change. This patch
should future proof this test.
Signed-off-by: Cyril Bur <cyril...@gmail.com>
---
Because the test no longer needs to use such a conservative time for
the busy wait, it actually runs much faster.
.../testing/selftests/powerpc/tm/tm-unavailable.c | 92 ++++++++++++++++++++--
1 file changed, 84 insertions(+), 8 deletions(-)
diff --git a/tools/testing/selftests/powerpc/tm/tm-unavailable.c
b/tools/testing/selftests/powerpc/tm/tm-unavailable.c
index e6a0fad2bfd0..54aeb7a7fbb1 100644
--- a/tools/testing/selftests/powerpc/tm/tm-unavailable.c
+++ b/tools/testing/selftests/powerpc/tm/tm-unavailable.c
@@ -33,6 +33,11 @@
#define VEC_UNA_EXCEPTION 1
#define VSX_UNA_EXCEPTION 2
+#define ERR_RETRY 1
+#define ERR_ADJUST 2
+
+#define COUNTER_INCREMENT (0x1000000)
+
#define NUM_EXCEPTIONS 3
#define err_at_line(status, errnum, format, ...) \
error_at_line(status, errnum, __FILE__, __LINE__, format ##__VA_ARGS__)
@@ -45,6 +50,7 @@ struct Flags {
int touch_vec;
int result;
int exception;
+ uint64_t counter;
} flags;
bool expecting_failure(void)
@@ -87,14 +93,12 @@ void *ping(void *input)
* Expected values for vs0 and vs32 after a TM failure. They must never
* change, otherwise they got corrupted.
*/
+ long rc = 0;
uint64_t high_vs0 = 0x5555555555555555;
uint64_t low_vs0 = 0xffffffffffffffff;
uint64_t high_vs32 = 0x5555555555555555;
uint64_t low_vs32 = 0xffffffffffffffff;
- /* Counter for busy wait */
- uint64_t counter = 0x1ff000000;
-
/*
* Variable to keep a copy of CR register content taken just after we
* leave the transactional state.
@@ -217,7 +221,7 @@ void *ping(void *input)
[ex_fp] "i" (FP_UNA_EXCEPTION),
[ex_vec] "i" (VEC_UNA_EXCEPTION),
[ex_vsx] "i" (VSX_UNA_EXCEPTION),
- [counter] "r" (counter)
+ [counter] "r" (flags.counter)
: "cr0", "ctr", "v10", "vs0", "vs10", "vs3", "vs32", "vs33",
"vs34", "fr10"
@@ -232,14 +236,14 @@ void *ping(void *input)
if (expecting_failure() && !is_failure(cr_)) {
printf("\n\tExpecting the transaction to fail, %s",
"but it didn't\n\t");
- flags.result++;
+ rc = ERR_ADJUST;
}
/* Check if we were not expecting a failure and a it occurred. */
if (!expecting_failure() && is_failure(cr_)) {
printf("\n\tUnexpected transaction failure 0x%02lx\n\t",
failure_code());
- return (void *) -1;
+ rc = ERR_RETRY;
}
/*
@@ -249,7 +253,7 @@ void *ping(void *input)
if (is_failure(cr_) && !failure_is_unavailable()) {
printf("\n\tUnexpected failure cause 0x%02lx\n\t",
failure_code());
- return (void *) -1;
+ rc = ERR_RETRY;
}
/* 0x4 is a success and 0xa is a fail. See comment in is_failure(). */
@@ -276,7 +280,7 @@ void *ping(void *input)
putchar('\n');
- return NULL;
+ return (void *)rc;
}
/* Thread to force context switch */
@@ -291,6 +295,55 @@ void *pong(void *not_used)
sched_yield();
}
+static void flags_set_counter(struct Flags *flags)
+{
+ uint64_t cr_;
+ int count = 0;
+
+ do {
+ if (count == 0)
+ printf("\tTrying 0x%08" PRIx64 "... ", flags->counter);
+ else
+ printf("%d, ", count);
+ fflush(stdout);
+ asm (
+ /*
+ * Wait an amount of context switches so
+ * load_fp and load_vec overflow and MSR.FP,
+ * MSR.VEC, and MSR.VSX become zero (off).
+ */
+ " mtctr %[counter] ;"
+
+ /* Decrement CTR branch if CTR non zero. */
+ "1: bdnz 1b ;"
+ " tbegin. ;"
+ " beq tfail ;"
+
+ /* Get a facility unavailable */
+ " fadd 10, 10, 10 ;"
+ " tend. ;"
+ "tfail: ;"
+
+ /*
+ * Give CR back to C so that it can check what
+ * happened.
+ */
+ " mfcr %[cr_] ;"
+
+ : [cr_] "+r" (cr_)
+ : [counter] "r" (flags->counter)
+ : "cr0", "ctr", "fr10"
+ );
+ count++;
+ if (!is_failure(cr_) || !failure_is_unavailable()) {
+ count = 0;
+ flags->counter += COUNTER_INCREMENT;
+ putchar('\n');
+ }
+ } while (count < 3);
+ printf("3\n");
+}
+
/* Function that creates a thread and launches the "ping" task. */
void test_fp_vec(int fp, int vec, pthread_attr_t *attr)
{
@@ -322,6 +375,17 @@ void test_fp_vec(int fp, int vec, pthread_attr_t *attr)
if (rc)
pr_err(rc, "pthread_join");
+ if ((long)ret_value == ERR_ADJUST) {
+ printf("Adjusting the facility unavailable spin
time...\n");
+ /*
+ * Be a bit more agressive just now - we'd
+ * really like to have it work
+ */
+ flags.counter += (2 * COUNTER_INCREMENT);
+ flags_set_counter(&flags);
+ printf("Now using 0x%08" PRIx64 "\n", flags.counter);
+ }
+
retries--;
} while (ret_value != NULL && retries);
@@ -340,6 +404,18 @@ int main(int argc, char **argv)
pthread_attr_t attr;
cpu_set_t cpuset;
+ /*
+ * Default counter for busy wait.
+ * 0x18000000 is a good baseline determined by experimentation
+ * on a POWER8
+ * The autodetecting code will bump it up if it too low.
+ */
+ flags.counter = 0x18000000;
+
+ printf("Testing required spin time required for facility
unavailable...\n");
+ flags_set_counter(&flags);
+ printf("Spin time required for a reliable facility unavailable TM
failure: 0x%" PRIx64 "\n",
+ flags.counter);
/* Set only CPU 0 in the mask. Both threads will be bound to CPU 0. */
CPU_ZERO(&cpuset);
CPU_SET(0, &cpuset);
--
2.15.0
