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    SubjectRe: [PATCH v2 08/11] drivers/base/test/test_async_driver_probe: convert to use counter_atomic32
    On Tue, Oct 06, 2020 at 02:44:39PM -0600, Shuah Khan wrote:
    > counter_atomic* is introduced to be used when a variable is used as
    > a simple counter and doesn't guard object lifetimes. This clearly
    > differentiates atomic_t usages that guard object lifetimes.
    >
    > counter_atomic* variables will wrap around to 0 when it overflows and
    > should not be used to guard resource lifetimes, device usage and
    > open counts that control state changes, and pm states.
    >
    > atomic_t variables used to count errors, warns, keep track of timeout,
    > and async completion are counters.
    >
    > Unsure overflow is a concern for timeout and async completion, and there
    > are no checks for overflow to hold them to upper bounds. Overflow and
    > wrap around doesn't impact errors, and warns.
    >
    > Convert them to use counter_atomic32.
    >
    > This conversion doesn't change the overflow wrap around behavior.
    >
    > Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    > Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
    > ---
    > drivers/base/test/test_async_driver_probe.c | 23 ++++++++++++---------
    > 1 file changed, 13 insertions(+), 10 deletions(-)
    >
    > diff --git a/drivers/base/test/test_async_driver_probe.c b/drivers/base/test/test_async_driver_probe.c
    > index 3bb7beb127a9..e969c1b09426 100644
    > --- a/drivers/base/test/test_async_driver_probe.c
    > +++ b/drivers/base/test/test_async_driver_probe.c
    > @@ -14,11 +14,12 @@
    > #include <linux/numa.h>
    > #include <linux/nodemask.h>
    > #include <linux/topology.h>
    > +#include <linux/counters.h>
    >
    > #define TEST_PROBE_DELAY (5 * 1000) /* 5 sec */
    > #define TEST_PROBE_THRESHOLD (TEST_PROBE_DELAY / 2)
    >
    > -static atomic_t warnings, errors, timeout, async_completed;
    > +static struct counter_atomic32 warnings, errors, timeout, async_completed;

    While it's currently harmless, this should likely be using
    COUNTER_ATOMIC_INIT(0)s...

    >
    > static int test_probe(struct platform_device *pdev)
    > {
    > @@ -29,9 +30,9 @@ static int test_probe(struct platform_device *pdev)
    > * have then report it as an error, otherwise we wil sleep for the
    > * required amount of time and then report completion.
    > */
    > - if (atomic_read(&timeout)) {
    > + if (counter_atomic32_read(&timeout)) {
    > dev_err(dev, "async probe took too long\n");
    > - atomic_inc(&errors);
    > + counter_atomic32_inc(&errors);
    > } else {
    > dev_dbg(&pdev->dev, "sleeping for %d msecs in probe\n",
    > TEST_PROBE_DELAY);
    > @@ -48,10 +49,10 @@ static int test_probe(struct platform_device *pdev)
    > dev_to_node(dev) != numa_node_id()) {
    > dev_warn(dev, "NUMA node mismatch %d != %d\n",
    > dev_to_node(dev), numa_node_id());
    > - atomic_inc(&warnings);
    > + counter_atomic32_inc(&warnings);
    > }
    >
    > - atomic_inc(&async_completed);
    > + counter_atomic32_inc(&async_completed);
    > }
    >
    > return 0;
    > @@ -244,11 +245,12 @@ static int __init test_async_probe_init(void)
    > * Otherwise if they completed without errors or warnings then
    > * report successful completion.
    > */
    > - if (atomic_read(&async_completed) != async_id) {
    > + if (counter_atomic32_read(&async_completed) != async_id) {
    > pr_err("async events still pending, forcing timeout\n");
    > - atomic_inc(&timeout);
    > + counter_atomic32_inc(&timeout);
    > err = -ETIMEDOUT;
    > - } else if (!atomic_read(&errors) && !atomic_read(&warnings)) {
    > + } else if (!counter_atomic32_read(&errors) &&
    > + !counter_atomic32_read(&warnings)) {
    > pr_info("completed successfully\n");
    > return 0;
    > }
    > @@ -271,12 +273,13 @@ static int __init test_async_probe_init(void)
    > * errors or warnings being reported by the probe routine.
    > */
    > if (err)
    > - atomic_inc(&errors);
    > + counter_atomic32_inc(&errors);
    > else
    > err = -EINVAL;
    >
    > pr_err("Test failed with %d errors and %d warnings\n",
    > - atomic_read(&errors), atomic_read(&warnings));
    > + counter_atomic32_read(&errors),
    > + counter_atomic32_read(&warnings));
    >
    > return err;
    > }
    > --
    > 2.25.1
    >

    But yeah, this is otherwise just reporting and simple one-time synchronization.

    Reviewed-by: Kees Cook <keescook@chromium.org>

    --
    Kees Cook

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