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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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