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Simplify cgroup creation

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This commit is contained in:
Eelco Dolstra 2020-05-16 21:21:41 +02:00
parent 7bdcf43b40
commit 570c443f56
3 changed files with 35 additions and 37 deletions
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35
src/libstore/build.cc
View file

@ -2375,30 +2375,17 @@ void DerivationGoal::startBuilder()
#if __linux__
if (useChroot) {
/* Create a cgroup. */
/* Create a systemd cgroup since that's the minimum required
by systemd-nspawn. */
// FIXME: do we want to use the parent cgroup? We should
// always use the same cgroup regardless of whether we're the
// daemon or run from a user session via sudo.
std::string msg;
std::vector<Path> cgroups;
for (auto & line : tokenizeString<std::vector<std::string>>(readFile("/proc/self/cgroup"), "\n")) {
static std::regex regex("([0-9]+):([^:]*):(.*)");
std::smatch match;
if (!std::regex_match(line, match, regex))
throw Error("invalid line '%s' in '/proc/self/cgroup'", line);
auto ourCgroups = getCgroups("/proc/self/cgroup");
auto systemdCgroup = ourCgroups["systemd"];
if (systemdCgroup == "")
throw Error("'systemd' cgroup does not exist");
/* We only create a systemd cgroup, since that's enough
for running systemd-nspawn. */
std::string name;
if (match[2] == "name=systemd")
name = "systemd";
//else if (match[2] == "")
// name = "unified";
else continue;
std::string cgroup = match[3];
auto hostCgroup = canonPath("/sys/fs/cgroup/" + name + "/" + cgroup);
auto hostCgroup = canonPath("/sys/fs/cgroup/systemd/" + systemdCgroup);
if (!pathExists(hostCgroup))
throw Error("expected cgroup directory '%s'", hostCgroup);
@ -2412,13 +2399,6 @@ void DerivationGoal::startBuilder()
chownToBuilder(childCgroup);
chownToBuilder(childCgroup + "/cgroup.procs");
if (name == "unified") {
chownToBuilder(childCgroup + "/cgroup.threads");
chownToBuilder(childCgroup + "/cgroup.subtree_control");
}
cgroups.push_back(childCgroup);
}
/* Set up private namespaces for the build:
@ -2545,7 +2525,6 @@ void DerivationGoal::startBuilder()
throw SysError("getting sandbox mount namespace");
/* Move the child into its own cgroup. */
for (auto & childCgroup : cgroups)
writeFile(childCgroup + "/cgroup.procs", fmt("%d", (pid_t) pid));
/* Signal the builder that we've updated its user namespace. */

17
src/libstore/cgroup.cc
View file

@ -9,6 +9,23 @@
namespace nix {
std::map<std::string, std::string> getCgroups(const Path & cgroupFile)
{
std::map<std::string, std::string> cgroups;
for (auto & line : tokenizeString<std::vector<std::string>>(readFile(cgroupFile), "\n")) {
static std::regex regex("([0-9]+):([^:]*):(.*)");
std::smatch match;
if (!std::regex_match(line, match, regex))
throw Error("invalid line '%s' in '%s'", line, cgroupFile);
std::string name = hasPrefix(match[2], "name=") ? std::string(match[2], 5) : match[2];
cgroups.insert_or_assign(name, match[3]);
}
return cgroups;
}
void destroyCgroup(const Path & cgroup)
{
for (auto & entry : readDirectory(cgroup)) {

2
src/libstore/cgroup.hh
View file

@ -6,6 +6,8 @@
namespace nix {
std::map<std::string, std::string> getCgroups(const Path & cgroupFile);
void destroyCgroup(const Path & cgroup);
}