Re: kern/57273: poll timeout is doubled when NetBSD is run inside QEMU

[Paul Goyette <paul%whooppee.com@localhost>]

The following reply was made to PR kern/57273; it has been noted by GNATS.

From: Paul Goyette <paul%whooppee.com@localhost>
To: gnats-bugs%netbsd.org@localhost
Cc: kern-bug-people%netbsd.org@localhost, gnats-admin%netbsd.org@localhost, netbsd-bugs%netbsd.org@localhost
Subject: Re: kern/57273: poll timeout is doubled when NetBSD is run inside
 QEMU
Date: Thu, 16 Mar 2023 10:10:50 -0700 (PDT)

 See kern/43997
 
 On Thu, 16 Mar 2023, roy%marples.name@localhost wrote:
 
 >> Number:         57273
 >> Category:       kern
 >> Synopsis:       poll timeout is doubled when NetBSD is run inside QEMU
 >> Confidential:   no
 >> Severity:       serious
 >> Priority:       medium
 >> Responsible:    kern-bug-people
 >> State:          open
 >> Class:          sw-bug
 >> Submitter-Id:   net
 >> Arrival-Date:   Thu Mar 16 16:55:00 +0000 2023
 >> Originator:     Roy Marples
 >> Release:        NetBSD-9.3
 >> Organization:
 >> Environment:
 > NetBSD netbsd9 9.3_STABLE NetBSD 9.3_STABLE (GENERIC) #0: Mon Mar 13 21:38:46 UTC 2023  mkrepro%mkrepro.NetBSD.org@localhost:/usr/src/sys/arch/amd64/compile/GENERIC amd64
 >> Description:
 > Testing dhcpcd timings in a NetBSD vm is impossible because the time to sleep with any polling mechanism (poll, pollts, kqueue) is doubled.
 > Outside the vm, on bare metal, it works fine.
 >> How-To-Repeat:
 > Install NetBSD to a qemu VM hosted on NetBSD.
 >
 > Reproducer:
 >
 > #include <poll.h>
 > #include <stdio.h>
 > #include <time.h>
 >
 > int
 > main(void)
 > {
 >        struct timespec ts = { .tv_sec = 10 };
 >        struct timespec start, end;
 >
 >        fprintf(stderr, "ppoll timeout %ld secs\n", ts.tv_sec);
 >        clock_gettime(CLOCK_MONOTONIC, &start);
 >        fprintf(stderr, "poll start is %ld, timeout is %ld, end should be %ld\n",
 >            start.tv_sec, ts.tv_sec, start.tv_sec + ts.tv_sec);
 >        pollts(NULL, 0, &ts, NULL);
 >        clock_gettime(CLOCK_MONOTONIC, &end);
 >        fprintf(stderr, "poll end is %ld, off by %ld secs\n",
 >            end.tv_sec, end.tv_sec - (start.tv_sec + ts.tv_sec));
 >        return 0;
 > }
 >> Fix:
 >
 >
 > !DSPAM:641349ef114062545387549!
 >
 >
 
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