[igt-dev] [PATCH i-g-t 01/01] lib/igt_pm: dump runtime pm status on timeout

[Hiatt, Don]

________________________________________
From: Konda, Vanshidhar R
Sent: Wednesday, October 02, 2019 1:56 PM
To: Hiatt, Don
Cc: igt-dev at lists.freedesktop.org
Subject: Re: [igt-dev] [PATCH i-g-t 01/01] lib/igt_pm: dump runtime pm status on timeout

On Wed, Oct 02, 2019 at 09:58:04AM -0700, don.hiatt at intel.com wrote:
>From: Don Hiatt <don.hiatt at intel.com>
>
>Display the runtime pm status if we timeout waiting for status.
>
>Signed-off-by: Don Hiatt <don.hiatt at intel.com>
>---
> lib/igt_pm.c | 16 ++++++++++++----
> lib/igt_pm.h |  2 +-
> 2 files changed, 13 insertions(+), 5 deletions(-)
>
>diff --git a/lib/igt_pm.c b/lib/igt_pm.c
>index 64ce240e093f..0d3561fdf821 100644
>--- a/lib/igt_pm.c
>+++ b/lib/igt_pm.c
>@@ -658,16 +658,17 @@ void igt_disable_runtime_pm(void)
>
> /**
>  * igt_get_runtime_pm_status:
>+ * @buf: buffer to place pm status string in
>+ * @len: length of buf
>  *
>  * Returns: The current runtime PM status.
>  */
>-enum igt_runtime_pm_status igt_get_runtime_pm_status(void)
>+enum igt_runtime_pm_status igt_get_runtime_pm_status(char *buf, int len)
> {
>       ssize_t n_read;
>-      char buf[32];
>
>       lseek(pm_status_fd, 0, SEEK_SET);
>-      n_read = read(pm_status_fd, buf, ARRAY_SIZE(buf) - 1);
>+      n_read = read(pm_status_fd, buf, len - 1);
>       igt_assert(n_read >= 0);

> May be we should add an assert here that makes sure n_read < len?
>
>Vanshi

Hi Vanshi,

read() can never return more than the size requested, see 'man 3 read':
  ssize_t pread(int fildes, void *buf, size_t nbyte, off_t offset);
  "This number shall never be greater than nbyte."

Thanks,

don


>       buf[n_read] = '\0';
>
>@@ -697,7 +698,14 @@ enum igt_runtime_pm_status igt_get_runtime_pm_status(void)
>  */
> bool igt_wait_for_pm_status(enum igt_runtime_pm_status status)
> {
>-      return igt_wait(igt_get_runtime_pm_status() == status, 10000, 100);
>+      bool ret;
>+      char buf[32];
>+
>+      ret = igt_wait(igt_get_runtime_pm_status(buf, ARRAY_SIZE(buf)) == status, 10000, 100);
>+      if (!ret)
>+              igt_warn("timeout: pm_status=%s", buf);
>+
>+      return ret;
> }
>
> /**
>diff --git a/lib/igt_pm.h b/lib/igt_pm.h
>index 7dc241749180..b2ff835e8a33 100644
>--- a/lib/igt_pm.h
>+++ b/lib/igt_pm.h
>@@ -49,7 +49,7 @@ enum igt_runtime_pm_status {
> bool igt_setup_runtime_pm(void);
> void igt_disable_runtime_pm(void);
> void igt_restore_runtime_pm(void);
>-enum igt_runtime_pm_status igt_get_runtime_pm_status(void);
>+enum igt_runtime_pm_status igt_get_runtime_pm_status(char *buf, int len);
> bool igt_wait_for_pm_status(enum igt_runtime_pm_status status);
> bool igt_pm_dmc_loaded(int debugfs);
> bool igt_pm_pc8_plus_residencies_enabled(int msr_fd);
>--
>2.20.1
>
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