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virnetdevmacvlan.c: Introduce mutex for macvlan creation

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Currently, after we removed the qemu driver lock, it may happen
that two or more threads will start up a machine with macvlan and
race over virNetDevMacVLanCreateWithVPortProfile(). However,
there's a racy section in which we are generating a sequence of
possible device names and detecting if they exits. If we found
one which doesn't we try to create a device with that name.
However, the other thread is doing just the same. Assume it will
succeed and we must therefore fail. If this happens more than 5
times (which in massive parallel startup surely will) we return
-1 without any error reported. This patch is a simple hack to
both of these problems. It introduces a mutex, so only one thread
will enter the section, and if it runs out of possibilities,
error is reported. Moreover, the number of retries is raised to 20.
This commit is contained in:
Michal Privoznik 2013-02-28 15:59:01 +01:00
parent 9c4ecb3e8e
commit 1cf97c87c0
1 changed files with 32 additions and 5 deletions
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37
src/util/virnetdevmacvlan.c
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@ -31,6 +31,7 @@
#include "virmacaddr.h"
#include "virutil.h"
#include "virerror.h"
#include "virthread.h"
#define VIR_FROM_THIS VIR_FROM_NET
@ -71,6 +72,19 @@ VIR_ENUM_IMPL(virNetDevMacVLanMode, VIR_NETDEV_MACVLAN_MODE_LAST,
# define MACVLAN_NAME_PREFIX "macvlan"
# define MACVLAN_NAME_PATTERN "macvlan%d"
virMutex virNetDevMacVLanCreateMutex;
static int virNetDevMacVLanCreateMutexOnceInit(void)
{
if (virMutexInit(&virNetDevMacVLanCreateMutex) < 0) {
virReportSystemError(errno, "%s", _("unable to init mutex"));
return -1;
}
return 0;
}
VIR_ONCE_GLOBAL_INIT(virNetDevMacVLanCreateMutex);
/**
* virNetDevMacVLanCreate:
*
@ -829,7 +843,7 @@ int virNetDevMacVLanCreateWithVPortProfile(const char *tgifname,
char ifname[IFNAMSIZ];
int retries, do_retry = 0;
uint32_t macvtapMode;
const char *cr_ifname;
const char *cr_ifname = NULL;
int ret;
int vf = -1;
@ -871,22 +885,35 @@ int virNetDevMacVLanCreateWithVPortProfile(const char *tgifname,
} else {
create_name:
retries = 5;
if (virNetDevMacVLanCreateMutexInitialize() < 0)
return -1;
virMutexLock(&virNetDevMacVLanCreateMutex);
for (c = 0; c < 8192; c++) {
snprintf(ifname, sizeof(ifname), pattern, c);
if ((ret = virNetDevExists(ifname)) < 0)
if ((ret = virNetDevExists(ifname)) < 0) {
virMutexUnlock(&virNetDevMacVLanCreateMutex);
return -1;
}
if (!ret) {
rc = virNetDevMacVLanCreate(ifname, type, macaddress, linkdev,
macvtapMode, &do_retry);
if (rc == 0)
if (rc == 0) {
cr_ifname = ifname;
break;
}
if (do_retry && --retries)
continue;
return -1;
break;
}
}
cr_ifname = ifname;
virMutexUnlock(&virNetDevMacVLanCreateMutex);
if (!cr_ifname) {
virReportError(VIR_ERR_OPERATION_FAILED, "%s",
_("Unable to create macvlan device"));
return -1;
}
}
if (virNetDevVPortProfileAssociate(cr_ifname,