On 03/30, David Rientjes wrote: > > On Tue, 30 Mar 2010, Oleg Nesterov wrote: > > > ->siglock is no longer needed to access task->signal, change > > oom_adjust_read() and oom_adjust_write() to read/write oom_adj > > lockless. > > > > Yes, this means that "echo 2 >oom_adj" and "echo 1 >oom_adj" > > can race and the second write can win, but I hope this is OK. > > Ok, but could you base this on -mm at > http://userweb.kernel.org/~akpm/mmotm/ since an additional tunable has > been added (oom_score_adj), which does the same thing? David, I just can't understand why oom-badness-heuristic-rewrite.patch duplicates the related code in fs/proc/base.c and why it preserves the deprecated signal->oom_adj. OK. Please forget about lock_task_sighand/signal issues. Can't we kill signal->oom_adj and create a single helper for both /proc/pid/{oom_adj,oom_score_adj} ? static ssize_t oom_any_adj_write(struct file *file, const char __user *buf, size_t count, bool deprecated_mode) { struct task_struct *task; char buffer[PROC_NUMBUF]; unsigned long flags; long oom_score_adj; int err; memset(buffer, 0, sizeof(buffer)); if (count > sizeof(buffer) - 1) count = sizeof(buffer) - 1; if (copy_from_user(buffer, buf, count)) return -EFAULT; err = strict_strtol(strstrip(buffer), 0, &oom_score_adj); if (err) return -EINVAL; if (depraceted_mode) { if (oom_score_adj == OOM_ADJUST_MAX) oom_score_adj = OOM_SCORE_ADJ_MAX; else oom_score_adj = (oom_score_adj * OOM_SCORE_ADJ_MAX) / -OOM_DISABLE; } if (oom_score_adj < OOM_SCORE_ADJ_MIN || oom_score_adj > OOM_SCORE_ADJ_MAX) return -EINVAL; task = get_proc_task(file->f_path.dentry->d_inode); if (!task) return -ESRCH; if (!lock_task_sighand(task, &flags)) { put_task_struct(task); return -ESRCH; } if (oom_score_adj < task->signal->oom_score_adj && !capable(CAP_SYS_RESOURCE)) { unlock_task_sighand(task, &flags); put_task_struct(task); return -EACCES; } task->signal->oom_score_adj = oom_score_adj; unlock_task_sighand(task, &flags); put_task_struct(task); return count; } This is just the current oom_score_adj_read() + "if (depraceted_mode)" which does oom_adj -> oom_score_adj conversion. Now, static ssize_t oom_adjust_write(...) { printk_once(KERN_WARNING "... deprecated ...\n"); return oom_any_adj_write(..., true); } static ssize_t oom_score_adj_write(...) { return oom_any_adj_write(..., false); } The same for oom_xxx_read(). What is the point to keep signal->oom_adj ? Oleg. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>