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author | David Rientjes <rientjes@google.com> | 2009-06-16 15:32:56 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-06-16 19:47:43 -0700 |
commit | 2ff05b2b4eac2e63d345fc731ea151a060247f53 (patch) | |
tree | 1840bc2d3b381eca5d39869499339b0fcc6eabbf /fs/proc | |
parent | c9e444103b5e7a5a3519f9913f59767f92e33baf (diff) | |
download | kernel_samsung_smdk4412-2ff05b2b4eac2e63d345fc731ea151a060247f53.zip kernel_samsung_smdk4412-2ff05b2b4eac2e63d345fc731ea151a060247f53.tar.gz kernel_samsung_smdk4412-2ff05b2b4eac2e63d345fc731ea151a060247f53.tar.bz2 |
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 <npiggin@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/proc')
-rw-r--r-- | fs/proc/base.c | 19 |
1 files changed, 16 insertions, 3 deletions
diff --git a/fs/proc/base.c b/fs/proc/base.c index 1539e63..3ce5ae9 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -1006,7 +1006,12 @@ static ssize_t oom_adjust_read(struct file *file, char __user *buf, if (!task) return -ESRCH; - oom_adjust = task->oomkilladj; + task_lock(task); + if (task->mm) + oom_adjust = task->mm->oom_adj; + else + oom_adjust = OOM_DISABLE; + task_unlock(task); put_task_struct(task); len = snprintf(buffer, sizeof(buffer), "%i\n", oom_adjust); @@ -1035,11 +1040,19 @@ static ssize_t oom_adjust_write(struct file *file, const char __user *buf, task = get_proc_task(file->f_path.dentry->d_inode); if (!task) return -ESRCH; - if (oom_adjust < task->oomkilladj && !capable(CAP_SYS_RESOURCE)) { + task_lock(task); + if (!task->mm) { + task_unlock(task); + put_task_struct(task); + return -EINVAL; + } + if (oom_adjust < task->mm->oom_adj && !capable(CAP_SYS_RESOURCE)) { + task_unlock(task); put_task_struct(task); return -EACCES; } - task->oomkilladj = oom_adjust; + task->mm->oom_adj = oom_adjust; + task_unlock(task); put_task_struct(task); if (end - buffer == 0) return -EIO; |