04/05/2021 21:12, Morten Brørup:

quoted

From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Thomas Monjalon
Sent: Tuesday, May 4, 2021 6:50 PM

29/04/2021 04:10, Min Hu (Connor):

quoted

Currently, the mp uses gettimeofday() API to get the time, and used

as

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timeout parameter.

But the time which gets from gettimeofday() API isn't monotonically
increasing. The process may fail if the system time is changed.

This fixes it by using clock_gettime() API with monotonic

attribution.

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Fixes: 783b6e54971d ("eal: add synchronous multi-process

communication")

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Fixes: f05e26051c15 ("eal: add IPC asynchronous request")
Cc: stable@dpdk.org

Signed-off-by: Chengwen Feng <redacted>
Signed-off-by: Min Hu (Connor) <redacted>
---

[...]

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--- a/lib/eal/common/eal_common_proc.c
+++ b/lib/eal/common/eal_common_proc.c
-	if (gettimeofday(&now, NULL) < 0) {
-		RTE_LOG(ERR, EAL, "Cannot get current time\n");
-		goto no_trigger;
-	}
-	ts_now.tv_nsec = now.tv_usec * 1000;
-	ts_now.tv_sec = now.tv_sec;
+	clock_gettime(CLOCK_MONOTONIC, &ts_now);

Why not testing the return value?

Because it is guaranteed not to fail. Ref:
https://linux.die.net/man/3/clock_gettime
https://www.freebsd.org/cgi/man.cgi?query=clock_gettime

I see "return 0 for success, or -1 for failure".
Where is it said it cannot fail?

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I think this change would not be appropriate after -rc1.
If you agree, I will postpone to DPDK 21.08.

It does fix a serious bug, where IPC timeouts can incorrectly happen. And this is not a theoretical bug; I have seen errors happen due to using the wrong clock source in other projects.

However, I have no clue if these IPC library functions are important or not. So I have no qualified opinion about postponing the change.

I think nobody hit such bug with DPDK IPC.