On Mon, 2008-12-15 at 22:19 +0530, Gowrishankar M wrote:
> Below patch addresses a common solution for any place where a process
> should be checked if it is associated to caller namespace. At present,
> we use 'task_pid_vnr(t) > 0' to further proceed with task 't' in current
> namespace.
>
> To avoid applying this check in every code related to PID namespace,
> this patch reworks on iterative macros;for_each_process and do_each_thread.
>
> This patch can also reduce latency time on process list lookup inside the
> container, as we walk along pidmap, instead of every process in system.
>
> Signed-off-by: Gowrishankar M <gowrishanka...@in.ibm.com>
> ---
> include/linux/sched.h | 8 +++++---
> kernel/pid.c | 17 +++++++++++++++++
> 2 files changed, 22 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index 2e46189..8d3b520 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -1917,17 +1917,19 @@ static inline unsigned long wait_task_inactive(struct
> task_struct *p,
> }
> #endif
>
> -#define next_task(p) list_entry(rcu_dereference((p)->tasks.next), struct
> task_struct, tasks)
> +#include <linux/nsproxy.h>
> +#define next_task(p) pid_task(find_ge_tgid(task_pid_vnr(p) + 1,
> p->nsproxy->pid_ns), PIDTYPE_PID)
> +#define ns_init_task (current->nsproxy->pid_ns == &init_pid_ns ?
> next_task((&init_task)) : find_task_by_vpid(1))
Can you turn these into static inlines so that they're a bit more
readable?
> #define for_each_process(p) \
> - for (p = &init_task ; (p = next_task(p)) != &init_task ; )
> + for (p = ns_init_task ; p != NULL ; p = next_task(p))
>
> /*
> * Careful: do_each_thread/while_each_thread is a double loop so
> * 'break' will not work as expected - use goto instead.
> */
> #define do_each_thread(g, t) \
> - for (g = t = &init_task ; (g = t = next_task(g)) != &init_task ; ) do
> + for (g = t = ns_init_task ; g != NULL ; (g = t = next_task(g))) do
I have to wonder whether we should be changing this globally or adding a
new do_each_ns_thread() or something. Are you worried this will cause
some collateral damage?
> +struct pid *find_ge_tgid(int nr, struct pid_namespace *ns)
> +{
> + struct pid* pid;
> + struct task_struct* task;
> +
> +retry:
> + pid = find_ge_pid(nr, ns);
> + if (pid) {
> + task = pid_task(pid, PIDTYPE_PID);
> + if (!task || !has_group_leader_pid(task)) {
> + nr += 1;
> + goto retry;
> + }
> + }
> + return pid;
> +}
I might have written that loop a bit differently. Does this work? Is
it any more clear?
while (pid = find_ge_pid(nr, ns) {
task = pid_task(pid, PIDTYPE_PID);
if (task && has_group_leader_pid(task))
break;
nr++;
}
-- Dave
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