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library: add support for displaying LXC container name

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This commit adds a lxc container name to every proc_t.
If a process is not running in a container, then a '-'
will be provided, making such a field always sortable.

Unlike other proc_t character pointers, lxc containers
will find many duplicate shared values. So rather than
strdup 'em (with a later free required upon reuse), we
try to keep track of those already seen and share that
address among all tasks running within each container.

We rely on the lines in the task's cgroup subdirectory
which may initially seem somewhat unsophisticated. But
the lxc library itself uses a similar approach when it
is called to list active containers. In that case, the
/proc/net/unix directory is parsed for the '/lxc' eye-
catcher, with potential complications from hashed path
and names that are too long (something we don't face).

[ too bad docker abandoned lxc - our commit won't do ]
[ anything for the users of those kind of containers ]

Reference(s):
https://bugs.launchpad.net/ubuntu/+source/lxc/+bug/1424253
https://bugs.launchpad.net/ubuntu/+source/procps/+bug/1424253

Signed-off-by: Jim Warner <james.warner@comcast.net>
This commit is contained in:
Jim Warner 2015-06-13 00:00:00 -05:00 committed by Craig Small
parent 96bce4e11e
commit 0557504f9c
2 changed files with 69 additions and 0 deletions
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66
proc/readproc.c
View File

@ -816,6 +816,64 @@ int read_cmdline(char *restrict const dst, unsigned sz, unsigned pid) {
}
// Provide the means to value proc_t.lxcname (perhaps only with "-") while
// tracking all names already seen thus avoiding the overhead of repeating
// malloc() and free() calls.
static const char *lxc_containers (const char *path) {
static struct utlbuf_s ub = { NULL, 0 }; // util buffer for whole cgroup
static char lxc_none[] = "-";
/*
try to locate the lxc delimiter eyecatcher somewhere in a task's cgroup
directory -- the following are from nested privileged plus unprivileged
containers, where the '/lxc/' delimiter precedes the container name ...
10:cpuset:/lxc/lxc-P/lxc/lxc-P-nested
10:cpuset:/user.slice/user-1000.slice/session-c2.scope/lxc/lxc-U/lxc/lxc-U-nested
... some minor complications are the potential addition of more cgroups
for a controller displacing the lxc name (normally last on a line), and
environments with unexpected /proc/##/cgroup ordering/contents as with:
10:cpuset:/lxc/lxc-P/lxc/lxc-P-nested/MY-NEW-CGROUP
or
2:name=systemd:/
1:cpuset,cpu,cpuacct,devices,freezer,net_cls,blkio,perf_event,net_prio:/lxc/lxc-P
*/
if (file2str(path, "cgroup", &ub) > 0) {
static const char lxc_delm[] = "/lxc/";
char *p1;
if ((p1 = strstr(ub.buf, lxc_delm))) {
static struct lxc_ele {
struct lxc_ele *next;
const char *name;
} *anchor = NULL;
struct lxc_ele *ele = anchor;
char *p2;
if ((p2 = strchr(p1, '\n'))) // isolate a controller's line
*p2 = '\0';
do { // deal with nested containers
p2 = p1 + (sizeof(lxc_delm)-1);
p1 = strstr(p2, lxc_delm);
} while (p1);
if ((p1 = strchr(p2, '/'))) // isolate name only substring
*p1 = '\0';
while (ele) { // have we already seen a name
if (!strcmp(ele->name, p2))
return ele->name; // return just a recycled name
ele = ele->next;
}
ele = (struct lxc_ele *)xmalloc(sizeof(struct lxc_ele));
ele->name = xstrdup(p2);
ele->next = anchor; // push the new container name
anchor = ele;
return ele->name; // return a new container name
}
}
return lxc_none;
}
///////////////////////////////////////////////////////////////////////
/* These are some nice GNU C expression subscope "inline" functions.
* The can be used with arbitrary types and evaluate their arguments
* exactly once.
@ -939,6 +997,10 @@ static proc_t* simple_readproc(PROCTAB *restrict const PT, proc_t *restrict cons
if (unlikely(flags & PROC_FILLSYSTEMD)) // get sd-login.h stuff
sd2proc(p);
#endif
if (unlikely(flags & PROC_FILL_LXC)) // value the lxc name
p->lxcname = lxc_containers(path);
return p;
next_proc:
return NULL;
@ -1047,6 +1109,9 @@ static proc_t* simple_readtask(PROCTAB *restrict const PT, const proc_t *restric
sd2proc(t);
#endif
if (unlikely(flags & PROC_FILL_LXC)) // value the lxc name
t->lxcname = lxc_containers(path);
#ifdef QUICK_THREADS
} else {
t->size = p->size;
@ -1071,6 +1136,7 @@ static proc_t* simple_readtask(PROCTAB *restrict const PT, const proc_t *restric
t->sd_unit = p->sd_unit;
t->sd_uunit = p->sd_uunit;
#endif
t->lxcname = p->lxcname;
MK_THREAD(t);
}
#endif

3
proc/readproc.h
View File

@ -181,6 +181,8 @@ typedef struct proc_t {
*sd_unit, // n/a systemd system unit id
*sd_uunit; // n/a systemd user unit id
#endif
const char
*lxcname; // n/a lxc container name
} proc_t;
// PROCTAB: data structure holding the persistent information readproc needs
@ -292,6 +294,7 @@ extern proc_t * get_proc_stats(pid_t pid, proc_t *p);
#define PROC_FILLOOM 0x0800 // fill in proc_t oom_score and oom_adj
#define PROC_FILLNS 0x8000 // fill in proc_t namespace information
#define PROC_FILLSYSTEMD 0x80000 // fill in proc_t systemd information
#define PROC_FILL_LXC 0x800000 // fill in proc_t lxcname, if possible
#define PROC_LOOSE_TASKS 0x2000 // treat threads as if they were processes