From 2ff05b2b4eac2e63d345fc731ea151a060247f53 Mon Sep 17 00:00:00 2001 From: David Rientjes Date: Tue, 16 Jun 2009 15:32:56 -0700 Subject: oom: move oom_adj value from task_struct to mm_struct The per-task oom_adj value is a characteristic of its mm more than the task itself since it's not possible to oom kill any thread that shares the mm. If a task were to be killed while attached to an mm that could not be freed because another thread were set to OOM_DISABLE, it would have needlessly been terminated since there is no potential for future memory freeing. This patch moves oomkilladj (now more appropriately named oom_adj) from struct task_struct to struct mm_struct. This requires task_lock() on a task to check its oom_adj value to protect against exec, but it's already necessary to take the lock when dereferencing the mm to find the total VM size for the badness heuristic. This fixes a livelock if the oom killer chooses a task and another thread sharing the same memory has an oom_adj value of OOM_DISABLE. This occurs because oom_kill_task() repeatedly returns 1 and refuses to kill the chosen task while select_bad_process() will repeatedly choose the same task during the next retry. Taking task_lock() in select_bad_process() to check for OOM_DISABLE and in oom_kill_task() to check for threads sharing the same memory will be removed in the next patch in this series where it will no longer be necessary. Writing to /proc/pid/oom_adj for a kthread will now return -EINVAL since these threads are immune from oom killing already. They simply report an oom_adj value of OOM_DISABLE. Cc: Nick Piggin Cc: Rik van Riel Cc: Mel Gorman Signed-off-by: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/oom_kill.c | 34 ++++++++++++++++++++++------------ 1 file changed, 22 insertions(+), 12 deletions(-) (limited to 'mm') diff --git a/mm/oom_kill.c b/mm/oom_kill.c index a7b2460e922..b60913520ef 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -58,6 +58,7 @@ unsigned long badness(struct task_struct *p, unsigned long uptime) unsigned long points, cpu_time, run_time; struct mm_struct *mm; struct task_struct *child; + int oom_adj; task_lock(p); mm = p->mm; @@ -65,6 +66,7 @@ unsigned long badness(struct task_struct *p, unsigned long uptime) task_unlock(p); return 0; } + oom_adj = mm->oom_adj; /* * The memory size of the process is the basis for the badness. @@ -148,15 +150,15 @@ unsigned long badness(struct task_struct *p, unsigned long uptime) points /= 8; /* - * Adjust the score by oomkilladj. + * Adjust the score by oom_adj. */ - if (p->oomkilladj) { - if (p->oomkilladj > 0) { + if (oom_adj) { + if (oom_adj > 0) { if (!points) points = 1; - points <<= p->oomkilladj; + points <<= oom_adj; } else - points >>= -(p->oomkilladj); + points >>= -(oom_adj); } #ifdef DEBUG @@ -251,8 +253,12 @@ static struct task_struct *select_bad_process(unsigned long *ppoints, *ppoints = ULONG_MAX; } - if (p->oomkilladj == OOM_DISABLE) + task_lock(p); + if (p->mm && p->mm->oom_adj == OOM_DISABLE) { + task_unlock(p); continue; + } + task_unlock(p); points = badness(p, uptime.tv_sec); if (points > *ppoints || !chosen) { @@ -304,8 +310,7 @@ static void dump_tasks(const struct mem_cgroup *mem) } printk(KERN_INFO "[%5d] %5d %5d %8lu %8lu %3d %3d %s\n", p->pid, __task_cred(p)->uid, p->tgid, mm->total_vm, - get_mm_rss(mm), (int)task_cpu(p), p->oomkilladj, - p->comm); + get_mm_rss(mm), (int)task_cpu(p), mm->oom_adj, p->comm); task_unlock(p); } while_each_thread(g, p); } @@ -367,8 +372,12 @@ static int oom_kill_task(struct task_struct *p) * Don't kill the process if any threads are set to OOM_DISABLE */ do_each_thread(g, q) { - if (q->mm == mm && q->oomkilladj == OOM_DISABLE) + task_lock(q); + if (q->mm == mm && q->mm && q->mm->oom_adj == OOM_DISABLE) { + task_unlock(q); return 1; + } + task_unlock(q); } while_each_thread(g, q); __oom_kill_task(p, 1); @@ -393,10 +402,11 @@ static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order, struct task_struct *c; if (printk_ratelimit()) { - printk(KERN_WARNING "%s invoked oom-killer: " - "gfp_mask=0x%x, order=%d, oomkilladj=%d\n", - current->comm, gfp_mask, order, current->oomkilladj); task_lock(current); + printk(KERN_WARNING "%s invoked oom-killer: " + "gfp_mask=0x%x, order=%d, oom_adj=%d\n", + current->comm, gfp_mask, order, + current->mm ? current->mm->oom_adj : OOM_DISABLE); cpuset_print_task_mems_allowed(current); task_unlock(current); dump_stack(); -- cgit v1.2.3