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SubjectRe: [PATCH] coredump: kill mm->core_done
On 07/15, Oleg Nesterov wrote:
>
> + for (;;) {
> + set_task_state(tsk, TASK_UNINTERRUPTIBLE);
> + if (!self.task) /* see coredump_finish() */
> + break;
> + schedule();
> + }
> + __set_task_state(tsk, TASK_UNINTERRUPTIBLE);
^^^^^^^^^^^^^^^^^^^^
Ugh, sorry, this should be TASK_RUNNING. Please find the fixed patch below.


[PATCH] coredump: kill mm->core_done

Now that we have core_state->dumper list we can use it to wake up the
sub-threads waiting for the coredump completion.

This uglifies the code and .text grows by 47 bytes, but otoh mm_struct
lessens by sizeof(struct completion). Also, with this change we can
decouple exit_mm() from the coredumping code.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>

include/linux/mm_types.h | 4 +---
kernel/exit.c | 8 +++++++-
fs/exec.c | 25 ++++++++++++++++++++++---
3 files changed, 30 insertions(+), 7 deletions(-)

--- 26-rc2/include/linux/mm_types.h~5_KILL_CORE_DONE 2008-07-13 18:28:36.000000000 +0400
+++ 26-rc2/include/linux/mm_types.h 2008-07-15 17:06:58.000000000 +0400
@@ -229,9 +229,7 @@ struct mm_struct {

unsigned long flags; /* Must use atomic bitops to access the bits */

- /* coredumping support */
- struct core_state *core_state;
- struct completion core_done;
+ struct core_state *core_state; /* coredumping support */

/* aio bits */
rwlock_t ioctx_list_lock; /* aio lock */
--- 26-rc2/kernel/exit.c~5_KILL_CORE_DONE 2008-07-13 19:58:19.000000000 +0400
+++ 26-rc2/kernel/exit.c 2008-07-15 20:17:28.000000000 +0400
@@ -680,7 +680,13 @@ static void exit_mm(struct task_struct *
if (atomic_dec_and_test(&core_state->nr_threads))
complete(&core_state->startup);

- wait_for_completion(&mm->core_done);
+ for (;;) {
+ set_task_state(tsk, TASK_UNINTERRUPTIBLE);
+ if (!self.task) /* see coredump_finish() */
+ break;
+ schedule();
+ }
+ __set_task_state(tsk, TASK_RUNNING);
down_read(&mm->mmap_sem);
}
atomic_inc(&mm->mm_count);
--- 26-rc2/fs/exec.c~5_KILL_CORE_DONE 2008-07-13 18:43:39.000000000 +0400
+++ 26-rc2/fs/exec.c 2008-07-15 20:16:36.000000000 +0400
@@ -1597,7 +1597,6 @@ static int coredump_wait(int exit_code,
struct completion *vfork_done;
int core_waiters;

- init_completion(&mm->core_done);
init_completion(&core_state->startup);
core_state->dumper.task = tsk;
core_state->dumper.next = NULL;
@@ -1623,6 +1622,27 @@ fail:
return core_waiters;
}

+static void coredump_finish(struct mm_struct *mm)
+{
+ struct core_thread *curr, *next;
+ struct task_struct *task;
+
+ next = mm->core_state->dumper.next;
+ while ((curr = next) != NULL) {
+ next = curr->next;
+ task = curr->task;
+ /*
+ * see exit_mm(), curr->task must not see
+ * ->task == NULL before we read ->next.
+ */
+ smp_mb();
+ curr->task = NULL;
+ wake_up_process(task);
+ }
+
+ mm->core_state = NULL;
+}
+
/*
* set_dumpable converts traditional three-value dumpable to two flags and
* stores them into mm->flags. It modifies lower two bits of mm->flags, but
@@ -1807,8 +1827,7 @@ fail_unlock:
argv_free(helper_argv);

current->fsuid = fsuid;
- complete_all(&mm->core_done);
- mm->core_state = NULL;
+ coredump_finish(mm);
fail:
return retval;
}



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