[net] devlink: Add method for time-stamp on reporter's dump

[net] devlink: Add method for time-stamp on reporter's dump

[Aya Levin]

When setting the dump's time-stamp, use ktime_get_real in addition to
jiffies. This simplifies the user space implementation and bypasses
some inconsistent behavior with translating jiffies to current time.

Fixes: c8e1da0bf923 ("devlink: Add health report functionality")
Signed-off-by: Aya Levin <ayal@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
---
 include/uapi/linux/devlink.h | 2 ++
 net/core/devlink.c           | 6 ++++++
 2 files changed, 8 insertions(+)

diff --git a/include/uapi/linux/devlink.h b/include/uapi/linux/devlink.h
index ffc993256527..4dd4e4e7b19b 100644
--- a/include/uapi/linux/devlink.h
+++ b/include/uapi/linux/devlink.h
@@ -348,6 +348,8 @@ enum devlink_attr {
 	DEVLINK_ATTR_PORT_PCI_PF_NUMBER,	/* u16 */
 	DEVLINK_ATTR_PORT_PCI_VF_NUMBER,	/* u16 */
 
+	DEVLINK_ATTR_HEALTH_REPORTER_DUMP_TSPEC,
+
 	/* add new attributes above here, update the policy in devlink.c */
 
 	__DEVLINK_ATTR_MAX,
diff --git a/net/core/devlink.c b/net/core/devlink.c
index d3dbb904bf3b..b26875c4329b 100644
--- a/net/core/devlink.c
+++ b/net/core/devlink.c
@@ -4577,6 +4577,7 @@ struct devlink_health_reporter {
 	bool auto_recover;
 	u8 health_state;
 	u64 dump_ts;
+	struct timespec dump_real_ts;
 	u64 error_count;
 	u64 recovery_count;
 	u64 last_recovery_ts;
@@ -4749,6 +4750,7 @@ static int devlink_health_do_dump(struct devlink_health_reporter *reporter,
 		goto dump_err;
 
 	reporter->dump_ts = jiffies;
+	reporter->dump_real_ts = ktime_to_timespec(ktime_get_real());
 
 	return 0;
 
@@ -4911,6 +4913,10 @@ devlink_nl_health_reporter_fill(struct sk_buff *msg,
 			      jiffies_to_msecs(reporter->dump_ts),
 			      DEVLINK_ATTR_PAD))
 		goto reporter_nest_cancel;
+	if (reporter->dump_fmsg &&
+	    nla_put(msg, DEVLINK_ATTR_HEALTH_REPORTER_DUMP_TSPEC,
+		    sizeof(reporter->dump_real_ts), &reporter->dump_real_ts))
+		goto reporter_nest_cancel;
 
 	nla_nest_end(msg, reporter_attr);
 	genlmsg_end(msg, hdr);
-- 
2.14.1

Re: [net] devlink: Add method for time-stamp on reporter's dump

[Andrew Lunn]

On Thu, Aug 22, 2019 at 11:17:51AM +0300, Aya Levin wrote:
> When setting the dump's time-stamp, use ktime_get_real in addition to
> jiffies. This simplifies the user space implementation and bypasses
> some inconsistent behavior with translating jiffies to current time.

Hi Aya

Is this year 2038 safe? I don't know enough about this to answer the
question myself.

Thanks
	Andrew

Re: [net] devlink: Add method for time-stamp on reporter's dump

[Ido Schimmel]

On Thu, Aug 22, 2019 at 04:06:35PM +0200, Andrew Lunn wrote:
> On Thu, Aug 22, 2019 at 11:17:51AM +0300, Aya Levin wrote:
> > When setting the dump's time-stamp, use ktime_get_real in addition to
> > jiffies. This simplifies the user space implementation and bypasses
> > some inconsistent behavior with translating jiffies to current time.
> 
> Hi Aya
> 
> Is this year 2038 safe? I don't know enough about this to answer the
> question myself.

Hi Andrew,

Good point. 'struct timespec' is not considered year 2038 safe and
unfortunately I recently made the mistake of using it to communicate
timestamps to user space over netlink. :/ The code is still in net-next,
so I will fix it while I can.

Arnd, would it be acceptable to use 'struct __kernel_timespec' instead?

Thanks

Re: [net] devlink: Add method for time-stamp on reporter's dump

[Arnd Bergmann]

On Thu, Aug 22, 2019 at 7:40 PM Ido Schimmel <idosch@idosch.org> wrote:
> On Thu, Aug 22, 2019 at 04:06:35PM +0200, Andrew Lunn wrote:
> > On Thu, Aug 22, 2019 at 11:17:51AM +0300, Aya Levin wrote:
> > > When setting the dump's time-stamp, use ktime_get_real in addition to
> > > jiffies. This simplifies the user space implementation and bypasses
> > > some inconsistent behavior with translating jiffies to current time.
> >
> > Is this year 2038 safe? I don't know enough about this to answer the
> > question myself.
>
> Good point. 'struct timespec' is not considered year 2038 safe and
> unfortunately I recently made the mistake of using it to communicate
> timestamps to user space over netlink. :/ The code is still in net-next,
> so I will fix it while I can.
>
> Arnd, would it be acceptable to use 'struct __kernel_timespec' instead?

The in-kernel representation should just use 'timespec64' if you need
separate seconds and nanoseconds, you can convert that to
__kernel_timespec while copying to user space.

However, please consider two other points:

- for simplicity, the general recommendation is to use 64-bit nanoseconds
  without separate seconds for timestamps
- instead of CLOCK_REALTIME, you could use CLOCK_MONOTONIC
  timestamps that are not affected by clock_settime() or leap second jumps.

      Arnd