[libvirt] [PATCH] udev: only report a warning if udev_enumerate_scan_devices fails
Even if an error is reported by `udev_enumerate_scan_devices`, e.g. because a driver of a device has an bug, we can still enumerate all other devices. Additionally the documentation of udev_enumerate_scan_devices says that on success an integer >= 0 is returned (see man udev_enumerate_scan_devices(3)). Reviewed-by: Bjoern Walk <bwalk@linux.ibm.com> Signed-off-by: Marc Hartmayer <mhartmay@linux.ibm.com> --- src/node_device/node_device_udev.c | 9 ++------- 1 file changed, 2 insertions(+), 7 deletions(-) diff --git a/src/node_device/node_device_udev.c b/src/node_device/node_device_udev.c index 299f55260129..90168eb8a969 100644 --- a/src/node_device/node_device_udev.c +++ b/src/node_device/node_device_udev.c @@ -1480,13 +1480,8 @@ udevEnumerateDevices(struct udev *udev) if (udevEnumerateAddMatches(udev_enumerate) < 0) goto cleanup; - ret = udev_enumerate_scan_devices(udev_enumerate); - if (ret != 0) { - virReportError(VIR_ERR_INTERNAL_ERROR, - _("udev scan devices returned %d"), - ret); - goto cleanup; - } + if (udev_enumerate_scan_devices(udev_enumerate) < 0) + VIR_WARN("udev scan devices failed"); udev_list_entry_foreach(list_entry, udev_enumerate_get_list_entry(udev_enumerate)) { -- 2.17.0
On 2/13/19 7:38 AM, Marc Hartmayer wrote:
Even if an error is reported by `udev_enumerate_scan_devices`, e.g. because a driver of a device has an bug, we can still enumerate all other devices. Additionally the documentation of udev_enumerate_scan_devices says that on success an integer >= 0 is returned (see man udev_enumerate_scan_devices(3)).
Reviewed-by: Bjoern Walk <bwalk@linux.ibm.com> Signed-off-by: Marc Hartmayer <mhartmay@linux.ibm.com> --- src/node_device/node_device_udev.c | 9 ++------- 1 file changed, 2 insertions(+), 7 deletions(-)
Interesting - looking at many examples of udev_enumerate_scan_devices usage shows a lack of testing the return value and as is done here just using @udev_enumerate to add devices after the call. Eventually found some source code for enumerator_scan_devices_tags which I believe is what device_enumerator_scan_devices would call due to what our AddMatches does. It seems that code works until it finds an error, but still would return a partially enumerated list. Long way of saying I think this is fine... However, now @ret = -1 doesn't ever get changed, so the caller would still fail. So it's a nice way to test your other patch ;-)
diff --git a/src/node_device/node_device_udev.c b/src/node_device/node_device_udev.c index 299f55260129..90168eb8a969 100644 --- a/src/node_device/node_device_udev.c +++ b/src/node_device/node_device_udev.c @@ -1480,13 +1480,8 @@ udevEnumerateDevices(struct udev *udev) if (udevEnumerateAddMatches(udev_enumerate) < 0) goto cleanup;
- ret = udev_enumerate_scan_devices(udev_enumerate); - if (ret != 0) { - virReportError(VIR_ERR_INTERNAL_ERROR, - _("udev scan devices returned %d"), - ret); - goto cleanup; - } + if (udev_enumerate_scan_devices(udev_enumerate) < 0) + VIR_WARN("udev scan devices failed");
Either before or after this, set ret = 0... or change the default from -1 to 0 and only change if the AddMatches fails. I think the other patch would still be necessary since if udevEnumerateAddMatches fails, then wouldn't the issue of setting threadQuit still exist?
udev_list_entry_foreach(list_entry, udev_enumerate_get_list_entry(udev_enumerate)) {
BTW: Using udevProcessDeviceListEntry as the 'example' of not failing if an element of udev_enumerate is problematic, I think logically if we don't get a full list we'd be OK to continue as well. John
On Wed, Feb 13, 2019 at 03:56 PM +0100, John Ferlan <jferlan@redhat.com> wrote:
On 2/13/19 7:38 AM, Marc Hartmayer wrote:
Even if an error is reported by `udev_enumerate_scan_devices`, e.g. because a driver of a device has an bug, we can still enumerate all other devices. Additionally the documentation of udev_enumerate_scan_devices says that on success an integer >= 0 is returned (see man udev_enumerate_scan_devices(3)).
Reviewed-by: Bjoern Walk <bwalk@linux.ibm.com> Signed-off-by: Marc Hartmayer <mhartmay@linux.ibm.com> --- src/node_device/node_device_udev.c | 9 ++------- 1 file changed, 2 insertions(+), 7 deletions(-)
Interesting - looking at many examples of udev_enumerate_scan_devices usage shows a lack of testing the return value and as is done here just using @udev_enumerate to add devices after the call.
Eventually found some source code for enumerator_scan_devices_tags which I believe is what device_enumerator_scan_devices would call due to what our AddMatches does. It seems that code works until it finds an error, but still would return a partially enumerated list.
Yep, I’ve also looked at the source code. Unfortunately the behavior is not documented… I’ve also looked for 'udev_enumerate_get_list_entry' and it can handle NULL pointers.
Long way of saying I think this is fine... However, now @ret = -1 doesn't ever get changed, so the caller would still fail. So it's a nice way to test your other patch ;-)
Yes… I’ll send a v2.
diff --git a/src/node_device/node_device_udev.c b/src/node_device/node_device_udev.c index 299f55260129..90168eb8a969 100644 --- a/src/node_device/node_device_udev.c +++ b/src/node_device/node_device_udev.c @@ -1480,13 +1480,8 @@ udevEnumerateDevices(struct udev *udev) if (udevEnumerateAddMatches(udev_enumerate) < 0) goto cleanup;
- ret = udev_enumerate_scan_devices(udev_enumerate); - if (ret != 0) { - virReportError(VIR_ERR_INTERNAL_ERROR, - _("udev scan devices returned %d"), - ret); - goto cleanup; - } + if (udev_enumerate_scan_devices(udev_enumerate) < 0) + VIR_WARN("udev scan devices failed");
Either before or after this, set ret = 0... or change the default from -1 to 0 and only change if the AddMatches fails.
I’ll set 'ret = 0;' at the end.
I think the other patch would still be necessary since if udevEnumerateAddMatches fails, then wouldn't the issue of setting threadQuit still exist?
udev_list_entry_foreach(list_entry, udev_enumerate_get_list_entry(udev_enumerate)) {
BTW: Using udevProcessDeviceListEntry as the 'example' of not failing if an element of udev_enumerate is problematic, I think logically if we don't get a full list we'd be OK to continue as well.
I agree.
John
-- Kind regards / Beste Grüße Marc Hartmayer IBM Deutschland Research & Development GmbH Vorsitzende des Aufsichtsrats: Matthias Hartmann Geschäftsführung: Dirk Wittkopp Sitz der Gesellschaft: Böblingen Registergericht: Amtsgericht Stuttgart, HRB 243294
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