From: "Stojaczyk, Dariusz" <dariusz.stojaczyk@intel.com>
To: "Gaëtan Rivet" <gaetan.rivet@6wind.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>,
"thomas@monjalon.net" <thomas@monjalon.net>
Subject: Re: [dpdk-dev] [PATCH v2] dev: don't remove devargs that are still referenced
Date: Thu, 22 Nov 2018 12:54:58 +0000 [thread overview]
Message-ID: <FBE7E039FA50BF47A673AD0BD3CD56A8462330D5@HASMSX105.ger.corp.intel.com> (raw)
In-Reply-To: <20181122095420.kmxulb6jpwblbkbd@bidouze.vm.6wind.com>
> -----Original Message-----
> From: Gaëtan Rivet [mailto:gaetan.rivet@6wind.com]
> Sent: Thursday, November 22, 2018 10:54 AM
> To: Stojaczyk, Dariusz <dariusz.stojaczyk@intel.com>
> Cc: dev@dpdk.org; thomas@monjalon.net
> Subject: Re: [PATCH v2] dev: don't remove devargs that are still referenced
>
> On Wed, Nov 21, 2018 at 08:38:27PM +0100, Darek Stojaczyk wrote:
> > Even if a device failed to plug, it's still a device
> > object that references the devargs. Those devargs will
> > be freed automatically together with the device, but
> > freeing them any earlier - like it's done in the hotplug
> > error handling path right now - will give us a dangling
> > pointer and a segfault scenario.
> >
> > Consider the following case:
> > * secondary process receives the hotplug request IPC message
> > * devargs are either created or updated
> > * the bus is scanned
> > * a new device object is created with the latest devargs
> > * the device can't be plugged for whatever reason,
> > bus->plug returns error
> > * the devargs are freed, even though they're still referenced
> > by the device object on the bus
> >
> > For PCI devices, the generic device name comes from
> > a buffer within the devargs. Freeing those will make
> > EAL segfault whenever the device name is checked.
> >
> > This patch just prevents the hotplug error handling
> > path from removing the devargs when there's a device
> > that references them. This is done by simply exiting
> > early from the hotplug function. As mentioned in the
> > beginning, those devargs will be freed later, together
> > with the device itself.
> >
>
> This seems ok in conjunction with Thomas' patch on overwriting devargs
> on insertion.
>
> The only place a device will be freed is the unplug bus ops, it already
> does remove the device devargs.
>
> > Fixes: 7e8b26650146 ("eal: fix hotplug add / remove")
> > Cc: gaetan.rivet@6wind.com
> > Cc: thomas@monjalon.net
> >
> > Signed-off-by: Darek Stojaczyk <dariusz.stojaczyk@intel.com>
> > ---
> > lib/librte_eal/common/eal_common_dev.c | 9 ++++-----
> > 1 file changed, 4 insertions(+), 5 deletions(-)
> >
> > diff --git a/lib/librte_eal/common/eal_common_dev.c
> b/lib/librte_eal/common/eal_common_dev.c
> > index 1fdc9ab17..b6fc5e437 100644
> > --- a/lib/librte_eal/common/eal_common_dev.c
> > +++ b/lib/librte_eal/common/eal_common_dev.c
> > @@ -169,11 +169,10 @@ local_dev_probe(const char *devargs, struct
> rte_device **new_dev)
> >
> > ret = dev->bus->plug(dev);
> > if (ret) {
> > - if (rte_dev_is_probed(dev)) /* if already succeeded earlier
> */
> > - return ret; /* no rollback */
> > - RTE_LOG(ERR, EAL, "Driver cannot attach the device (%s)\n",
> > - dev->name);
> > - goto err_devarg;
> > + if (!rte_dev_is_probed(dev)) /* if hasn't succeeded earlier */
> > + RTE_LOG(ERR, EAL, "Driver cannot attach the device
> (%s)\n",
> > + dev->name);
>
> Maybe a comment here to describe that the devargs is still the
> responsibility of the rte_device and should not be removed.
Ack, I'll do that.
>
> > + return ret;
> > }
> >
> > *new_dev = dev;
> > --
> > 2.17.1
> >
>
> --
> Gaëtan Rivet
> 6WIND
next prev parent reply other threads:[~2018-11-22 12:55 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-21 18:37 [dpdk-dev] [PATCH] " Darek Stojaczyk
2018-11-21 18:55 ` Thomas Monjalon
2018-11-21 19:38 ` [dpdk-dev] [PATCH v2] " Darek Stojaczyk
2018-11-22 9:54 ` Gaëtan Rivet
2018-11-22 12:54 ` Stojaczyk, Dariusz [this message]
2018-11-23 15:43 ` [dpdk-dev] [PATCH v3] " Darek Stojaczyk
2018-11-23 17:04 ` Maxime Coquelin
2018-11-23 21:45 ` Stojaczyk, Dariusz
2018-11-25 12:46 ` Thomas Monjalon
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