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SubjectRe: [PATCH] [JFFS2] Move jffs2_gcd_mtd threads to the new kthread API
On Fri, 29 May 2009 11:19:41 +0300
Gerard Lledo <gerard.lledo@gmail.com> wrote:

> kernel_thread() is being depracated. This patch moves the jffs2 garbage
> collecting thread to the new kthread API with the minimal impact.
>
> Signed-off-by: Gerard Lledo <gerard.lledo@gmail.com>
> ---
> fs/jffs2/background.c | 22 ++++++++++++++--------
> 1 files changed, 14 insertions(+), 8 deletions(-)
>
> diff --git a/fs/jffs2/background.c b/fs/jffs2/background.c
> index e958010..077fa65 100644
> --- a/fs/jffs2/background.c
> +++ b/fs/jffs2/background.c
> @@ -15,6 +15,7 @@
> #include <linux/completion.h>
> #include <linux/sched.h>
> #include <linux/freezer.h>
> +#include <linux/kthread.h>
> #include "nodelist.h"
>
>
> @@ -31,7 +32,7 @@ void jffs2_garbage_collect_trigger(struct jffs2_sb_info *c)
> /* This must only ever be called when no GC thread is currently running */
> int jffs2_start_garbage_collect_thread(struct jffs2_sb_info *c)
> {
> - pid_t pid;
> + struct task_struct *tsk;
> int ret = 0;
>
> BUG_ON(c->gc_task);
> @@ -39,15 +40,16 @@ int jffs2_start_garbage_collect_thread(struct jffs2_sb_info *c)
> init_completion(&c->gc_thread_start);
> init_completion(&c->gc_thread_exit);
>
> - pid = kernel_thread(jffs2_garbage_collect_thread, c, CLONE_FS|CLONE_FILES);
> - if (pid < 0) {
> - printk(KERN_WARNING "fork failed for JFFS2 garbage collect thread: %d\n", -pid);
> + tsk = kthread_create(jffs2_garbage_collect_thread, c, "jffs2_gcd_mtd%d", c->mtd->index);
> + if (IS_ERR(tsk)) {
> + printk(KERN_WARNING "fork failed for JFFS2 garbage collect thread: %ld\n", -PTR_ERR(tsk));
> complete(&c->gc_thread_exit);
> - ret = pid;
> + ret = PTR_ERR(tsk);
> } else {
> - /* Wait for it... */
> - D1(printk(KERN_DEBUG "JFFS2: Garbage collect thread is pid %d\n", pid));
> + D1(printk(KERN_DEBUG "JFFS2: Garbage collect thread is pid %d\n", tsk->pid));
> + wake_up_process(tsk);
> wait_for_completion(&c->gc_thread_start);
> + ret = tsk->pid;
> }

A simple kthread_run() would be preferable here. The code presently
sort-of open-codes it.

> return ret;

Also, manipulating kernel threads via their pids is atypical and
inefficient. In-kernel it is better to refer to threads via their
task_struct*.

Fortunately all callers of this function ignore its return value so I
expect we can simply change it to be void-returning. But that's a
cleanup which would best be done in a spearate patch.

> @@ -71,7 +73,6 @@ static int jffs2_garbage_collect_thread(void *_c)
> {
> struct jffs2_sb_info *c = _c;
>
> - daemonize("jffs2_gcd_mtd%d", c->mtd->index);
> allow_signal(SIGKILL);
> allow_signal(SIGSTOP);
> allow_signal(SIGCONT);
> @@ -107,6 +108,11 @@ static int jffs2_garbage_collect_thread(void *_c)
> * the GC thread get there first. */
> schedule_timeout_interruptible(msecs_to_jiffies(50));
>
> + if (kthread_should_stop()) {
> + D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): kthread_stop() called.\n"));
> + goto die;
> + }
> +
> /* Put_super will send a SIGKILL and then wait on the sem.
> */
> while (signal_pending(current) || freezing(current)) {




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