Messages in this thread Patch in this message | | | Date | Sun, 13 Jul 2008 21:22:57 +0400 | From | Oleg Nesterov <> | Subject | [PATCH 2/4] coredump: construct the list of coredumping threads at startup time |
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binfmt->core_dump() has to iterate over the all threads in system in order to find the coredumping threads and construct the list using the GFP_ATOMIC allocations.
With this patch each thread allocates the list node on exit_mm()'s stack and adds itself to the list.
This allows us to do further changes:
- simplify ->core_dump()
- change exit_mm() to clear ->mm first, then wait for ->core_done. this makes the coredumping process visible to oom_kill
- kill mm->core_done
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
include/linux/mm_types.h | 6 ++++++ fs/exec.c | 2 ++ kernel/exit.c | 15 ++++++++++++--- 3 files changed, 20 insertions(+), 3 deletions(-)
--- 26-rc2/include/linux/mm_types.h~2_CORE_THREAD 2008-06-16 18:00:08.000000000 +0400 +++ 26-rc2/include/linux/mm_types.h 2008-07-13 18:28:36.000000000 +0400 @@ -159,8 +159,14 @@ struct vm_area_struct { #endif }; +struct core_thread { + struct task_struct *task; + struct core_thread *next; +}; + struct core_state { atomic_t nr_threads; + struct core_thread dumper; struct completion startup; }; --- 26-rc2/fs/exec.c~2_CORE_THREAD 2008-07-13 17:47:28.000000000 +0400 +++ 26-rc2/fs/exec.c 2008-07-13 18:43:39.000000000 +0400 @@ -1599,6 +1599,8 @@ static int coredump_wait(int exit_code, init_completion(&mm->core_done); init_completion(&core_state->startup); + core_state->dumper.task = tsk; + core_state->dumper.next = NULL; core_waiters = zap_threads(tsk, mm, core_state, exit_code); up_write(&mm->mmap_sem); --- 26-rc2/kernel/exit.c~2_CORE_THREAD 2008-07-06 18:10:12.000000000 +0400 +++ 26-rc2/kernel/exit.c 2008-07-13 19:58:19.000000000 +0400 @@ -653,6 +653,7 @@ assign_new_owner: static void exit_mm(struct task_struct * tsk) { struct mm_struct *mm = tsk->mm; + struct core_state *core_state; mm_release(tsk, mm); if (!mm) @@ -665,11 +666,19 @@ static void exit_mm(struct task_struct * * group with ->mm != NULL. */ down_read(&mm->mmap_sem); - if (mm->core_state) { + core_state = mm->core_state; + if (core_state) { + struct core_thread self; up_read(&mm->mmap_sem); - if (atomic_dec_and_test(&mm->core_state->nr_threads)) - complete(&mm->core_state->startup); + self.task = tsk; + self.next = xchg(&core_state->dumper.next, &self); + /* + * Implies mb(), the result of xchg() must be visible + * to core_state->dumper. + */ + if (atomic_dec_and_test(&core_state->nr_threads)) + complete(&core_state->startup); wait_for_completion(&mm->core_done); down_read(&mm->mmap_sem);
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