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lxc: acquire a pidfile in the driver root directory

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When we allow multiple instances of the driver for the same user
account, using a separate root directory, we need to ensure mutual
exclusion. Use a pidfile to guarantee this.

In privileged libvirtd this ends up locking

   /var/run/libvirt/lxc/driver.pid

In unprivileged libvirtd this ends up locking

  /run/user/$UID/libvirt/lxc/run/driver.pid

NB, the latter can vary depending on $XDG_RUNTIME_DIR

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
This commit is contained in:
Daniel P. Berrangé 2019-05-23 11:34:08 +01:00
parent 59080d84c0
commit 64c5b6bc06
2 changed files with 12 additions and 0 deletions
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3
src/lxc/lxc_conf.h
View File

@ -70,6 +70,9 @@ struct _virLXCDriver {
* then lockless thereafter */
virLXCDriverConfigPtr config;
/* pid file FD, ensures two copies of the driver can't use the same root */
int lockFD;
/* Require lock to get a reference on the object,
* lockless access thereafter */
virCapsPtr caps;

9
src/lxc/lxc_driver.c
View File

@ -1559,6 +1559,7 @@ static int lxcStateInitialize(bool privileged,
if (VIR_ALLOC(lxc_driver) < 0)
return -1;
lxc_driver->lockFD = -1;
if (virMutexInit(&lxc_driver->lock) < 0) {
VIR_FREE(lxc_driver);
return -1;
@ -1605,6 +1606,10 @@ static int lxcStateInitialize(bool privileged,
goto cleanup;
}
if ((lxc_driver->lockFD =
virPidFileAcquire(cfg->stateDir, "driver", true, getpid())) < 0)
goto cleanup;
/* Get all the running persistent or transient configs first */
if (virDomainObjListLoadAllConfigs(lxc_driver->domains,
cfg->stateDir,
@ -1696,6 +1701,10 @@ static int lxcStateCleanup(void)
virObjectUnref(lxc_driver->caps);
virObjectUnref(lxc_driver->securityManager);
virObjectUnref(lxc_driver->xmlopt);
if (lxc_driver->lockFD != -1)
virPidFileRelease(lxc_driver->config->stateDir, "driver", lxc_driver->lockFD);
virObjectUnref(lxc_driver->config);
virMutexDestroy(&lxc_driver->lock);
VIR_FREE(lxc_driver);