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netpoll: Remove 4s sleep during carrier detection

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This patch removes the msleep(4s) during netpoll_setup() if the carrier
appears instantly.

Here are some scenarios where this workaround is counter-productive in
modern ages:

Servers which have BMC communicating over NC-SI via the same NIC as gets
used for netconsole. BMC will keep the PHY up, hence the carrier
appearing instantly.

The link is fibre, SERDES getting sync could happen within 0.1Hz, and
the carrier also appears instantly.

Other than that, if a driver is reporting instant carrier and then
losing it, this is probably a driver bug.

Reported-by: Michael van der Westhuizen <rmikey@meta.com>
Signed-off-by: Breno Leitao <leitao@debian.org>
Link: https://lore.kernel.org/r/20230125185230.3574681-1-leitao@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Breno Leitao 2023-01-25 10:52:30 -08:00 committed by Jakub Kicinski
parent b568d3072a
commit d8afe2f8a9
1 changed files with 1 additions and 11 deletions
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12
net/core/netpoll.c
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@ -682,7 +682,7 @@ int netpoll_setup(struct netpoll *np)
}
if (!netif_running(ndev)) {
unsigned long atmost, atleast;
unsigned long atmost;
np_info(np, "device %s not up yet, forcing it\n", np->dev_name);
@ -694,7 +694,6 @@ int netpoll_setup(struct netpoll *np)
}
rtnl_unlock();
atleast = jiffies + HZ/10;
atmost = jiffies + carrier_timeout * HZ;
while (!netif_carrier_ok(ndev)) {
if (time_after(jiffies, atmost)) {
@ -704,15 +703,6 @@ int netpoll_setup(struct netpoll *np)
msleep(1);
}
/* If carrier appears to come up instantly, we don't
* trust it and pause so that we don't pump all our
* queued console messages into the bitbucket.
*/
if (time_before(jiffies, atleast)) {
np_notice(np, "carrier detect appears untrustworthy, waiting 4 seconds\n");
msleep(4000);
}
rtnl_lock();
}