The new iterant kthread API allows to define a common checkpoint for
freezing, parking, termination, and even signal handling. It will allow
to maintain kthreads more easily and make the operations more reliable[*].
The kthread function is split into optional init(), func(), destroy() parts
where func() is called in a cycle. The common check point is after
each func() finishes. See kthread_iterant_fn() for more details.
func() does not need to call schedule(). Instead, we call
set_kthread_iterant_int_sleep() and let the generic code
to handle the sleeping properly.
There are few small functional changes:
+ SIGSTOP uses the standard handler and could not print debug
messages any longer
+ there is no need to enable or define sighandler for SIGCONT;
it is handled by prepare_signal() and could not get disabled
+ the debug message for default signal handler was removed; It is
handled in kernel_do_signal() a standard way. In reality, this
never happens because all signals are disabled except for the
four ones enabled by kthread_sigaction();
+ we call complete() instead of complete_and_exit(); do_exit() is
called in kthread() anyway after the function returns.
[*] In fact, there was a bug in the original code. It tried to process
a non-existing signal when the system was freezing. See the common
check for pending signal and freezing.
Signed-off-by: Petr Mladek <pmla...@suse.cz>
---
fs/jffs2/background.c | 156 ++++++++++++++++++++++++--------------------------
1 file changed, 74 insertions(+), 82 deletions(-)
diff --git a/fs/jffs2/background.c b/fs/jffs2/background.c
index 6af076b8f60f..50c16048ba2d 100644
--- a/fs/jffs2/background.c
+++ b/fs/jffs2/background.c
@@ -21,99 +21,86 @@
#include <linux/kthread.h>
#include "nodelist.h"
-static int jffs2_garbage_collect_thread(void *_c)
+static void jffs2_garbage_collect_thread_sighup(int sig)
+{
+ jffs2_dbg(1, "%s(): SIGHUP received\n", __func__);
+}
+
+static void jffs2_garbage_collect_thread_sigkill(int sig)
+{
+ jffs2_dbg(1, "%s(): SIGKILL received\n", __func__);
+ kthread_stop_current();
+}
+
+static void jffs2_garbage_collect_thread_init(void *_c)
{
struct jffs2_sb_info *c = _c;
- sigset_t hupmask;
- siginitset(&hupmask, sigmask(SIGHUP));
- allow_signal(SIGKILL);
- allow_signal(SIGSTOP);
- allow_signal(SIGCONT);
- allow_signal(SIGHUP);
+ kthread_sigaction(SIGKILL, jffs2_garbage_collect_thread_sigkill);
+ kthread_sigaction(SIGHUP, jffs2_garbage_collect_thread_sighup);
+ kthread_sigaction(SIGSTOP, KTHREAD_SIG_DFL);
c->gc_task = current;
complete(&c->gc_thread_start);
set_user_nice(current, 10);
+};
+
+static void jffs2_garbage_collect_thread_func(void *_c)
+{
+ struct jffs2_sb_info *c = _c;
+ sigset_t hupmask;
+
+ siginitset(&hupmask, sigmask(SIGHUP));
- set_freezable();
- for (;;) {
- sigprocmask(SIG_UNBLOCK, &hupmask, NULL);
- again:
- spin_lock(&c->erase_completion_lock);
- if (!jffs2_thread_should_wake(c)) {
- set_current_state (TASK_INTERRUPTIBLE);
- spin_unlock(&c->erase_completion_lock);
- jffs2_dbg(1, "%s(): sleeping...\n", __func__);
- schedule();
- } else {
- spin_unlock(&c->erase_completion_lock);
- }
- /* Problem - immediately after bootup, the GCD spends a lot
- * of time in places like jffs2_kill_fragtree(); so much so
- * that userspace processes (like gdm and X) are starved
- * despite plenty of cond_resched()s and renicing. Yield()
- * doesn't help, either (presumably because userspace and GCD
- * are generally competing for a higher latency resource -
- * disk).
- * This forces the GCD to slow the hell down. Pulling an
- * inode in with read_inode() is much preferable to having
- * the GC thread get there first. */
- schedule_timeout_interruptible(msecs_to_jiffies(50));
-
- if (kthread_should_stop()) {
- jffs2_dbg(1, "%s(): kthread_stop() called\n", __func__);
- goto die;
- }
-
- /* Put_super will send a SIGKILL and then wait on the sem.
- */
- while (signal_pending(current) || freezing(current)) {
- siginfo_t info;
- unsigned long signr;
-
- if (try_to_freeze())
- goto again;
-
- signr = dequeue_signal_lock(current, ¤t->blocked,
&info);
-
- switch(signr) {
- case SIGSTOP:
- jffs2_dbg(1, "%s(): SIGSTOP received\n",
- __func__);
- set_current_state(TASK_STOPPED);
- schedule();
- break;
-
- case SIGKILL:
- jffs2_dbg(1, "%s(): SIGKILL received\n",
- __func__);
- goto die;
-
- case SIGHUP:
- jffs2_dbg(1, "%s(): SIGHUP received\n",
- __func__);
- break;
- default:
- jffs2_dbg(1, "%s(): signal %ld received\n",
- __func__, signr);
- }
- }
- /* We don't want SIGHUP to interrupt us. STOP and KILL are OK
though. */
- sigprocmask(SIG_BLOCK, &hupmask, NULL);
-
- jffs2_dbg(1, "%s(): pass\n", __func__);
- if (jffs2_garbage_collect_pass(c) == -ENOSPC) {
- pr_notice("No space for garbage collection. Aborting GC
thread\n");
- goto die;
- }
+ spin_lock(&c->erase_completion_lock);
+ if (!jffs2_thread_should_wake(c)) {
+ set_kthread_iterant_int_sleep();
+ spin_unlock(&c->erase_completion_lock);
+ jffs2_dbg(1, "%s(): sleeping...\n", __func__);
+ return;
+ }
+ spin_unlock(&c->erase_completion_lock);
+
+ /* Problem - immediately after bootup, the GCD spends a lot
+ * of time in places like jffs2_kill_fragtree(); so much so
+ * that userspace processes (like gdm and X) are starved
+ * despite plenty of cond_resched()s and renicing. Yield()
+ * doesn't help, either (presumably because userspace and GCD
+ * are generally competing for a higher latency resource -
+ * disk).
+ * This forces the GCD to slow the hell down. Pulling an
+ * inode in with read_inode() is much preferable to having
+ * the GC thread get there first.
+ */
+ schedule_timeout_interruptible(msecs_to_jiffies(50));
+
+ if (kthread_should_stop()) {
+ jffs2_dbg(1, "%s(): kthread_stop() called\n", __func__);
+ return;
}
- die:
+
+ try_to_freeze();
+
+ /* We don't want SIGHUP to interrupt us. STOP and KILL are OK though. */
+ sigprocmask(SIG_BLOCK, &hupmask, NULL);
+
+ jffs2_dbg(1, "%s(): pass\n", __func__);
+ if (jffs2_garbage_collect_pass(c) == -ENOSPC) {
+ pr_notice("No space for garbage collection. Aborting GC
thread\n");
+ kthread_stop_current();
+ }
+ sigprocmask(SIG_UNBLOCK, &hupmask, NULL);
+}
+
+static void jffs2_garbage_collect_thread_destroy(void *_c)
+{
+ struct jffs2_sb_info *c = _c;
+
spin_lock(&c->erase_completion_lock);
c->gc_task = NULL;
spin_unlock(&c->erase_completion_lock);
- complete_and_exit(&c->gc_thread_exit, 0);
+ complete(&c->gc_thread_exit);
}
void jffs2_garbage_collect_trigger(struct jffs2_sb_info *c)
@@ -126,16 +113,21 @@ 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)
{
+ static struct kthread_iterant kti = {
+ .init = jffs2_garbage_collect_thread_init,
+ .func = jffs2_garbage_collect_thread_func,
+ .destroy = jffs2_garbage_collect_thread_destroy,
+ };
struct task_struct *tsk;
int ret = 0;
BUG_ON(c->gc_task);
+ kti.data = c;
init_completion(&c->gc_thread_start);
init_completion(&c->gc_thread_exit);
- tsk = kthread_run(jffs2_garbage_collect_thread, c,
- "jffs2_gcd_mtd%d", c->mtd->index);
+ tsk = kthread_iterant_run(&kti, "jffs2_gcd_mtd%d", c->mtd->index);
if (IS_ERR(tsk)) {
pr_warn("fork failed for JFFS2 garbage collect thread: %ld\n",
-PTR_ERR(tsk));
--
1.8.5.6
--
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