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ctrools: Rewrite task/threads stopping engine

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Stopping tasks with STOP and proceeding with SEIZE is actually excessive --
the SEIZE if enough. Moreover, just killing a task with STOP is also racy,
since task should be given some time to come to sleep before its proc
can be parsed.

Rewrite all this code to SEIZE task and all its threads from the very beginning.

With this we can distinguish stopped task state and migrate it properly (not
supported now, need to implement).

This thing however has one BIG problem -- after we SEIZE-d a task we should seize
it's threads, but we should do it in a loop -- reading /proc/pid/task and seizing
them again and again, until the contents of this dir stops changing (not done now).

Besides, after we seized a task and all its threads we cannot scan it's children
list once -- task can get reparented to init and any task's child can call clone
with CLONE_PARENT flag thus repopulating the children list of the already seized
task (not done also)

This patch is ugly, yes, but splitting it doesn't help to review it much, sorry :(

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
This commit is contained in:
Pavel Emelyanov
2012-02-01 17:03:51 +04:00
committed by Cyrill Gorcunov
parent 501d85193c
commit 6da51eee3f
9 changed files with 228 additions and 153 deletions
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30
proc_parse.c
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@@ -175,6 +175,36 @@ err_bogus_mapping:
goto err;
}
int parse_pid_stat_small(pid_t pid, int pid_dir, struct proc_pid_stat_small *s)
{
FILE *f;
char *tok;
int n;
f = fopen_proc(pid_dir, "stat");
if (f == NULL) {
pr_perror("Can't open %d's stat", pid);
return -1;
}
memset(s, 0, sizeof(*s));
n = fscanf(f, "%d " PROC_TASK_COMM_LEN_FMT " %c",
&s->pid, s->comm, &s->state);
if (n < 3) {
pr_err("Parsing %d's stat failed (#fields do not match)\n", pid);
return -1;
}
s->comm[PROC_TASK_COMM_LEN-1] = '\0';
tok = strchr(s->comm, ')');
if (tok)
*tok = '\0';
fclose(f);
return 0;
}
int parse_pid_stat(pid_t pid, int pid_dir, struct proc_pid_stat *s)
{
FILE *f;