The patch titled
freezer_cg: remove task_lock from freezer_fork()
has been added to the -mm tree. Its filename is
freezer_cg-remove-task_lock-from-freezer_fork.patch
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------------------------------------------------------
Subject: freezer_cg: remove task_lock from freezer_fork()
From: Li Zefan <lizf@xxxxxxxxxxxxxx>
In theory the task can be moved to another cgroup and the freezer will be
freed right after task_lock is dropped, so the lock results in zero
protection.
But in the case of freezer_fork() no lock is needed, since the task is not
in tasklist yet so it won't be moved to another cgroup, so task->cgroups
won't be changed or invalidated.
Signed-off-by: Li Zefan <lizf@xxxxxxxxxxxxxx>
Cc: Matt Helsley <matthltc@xxxxxxxxxx>
Cc: Cedric Le Goater <clg@xxxxxxxxxx>
Cc: "Serge E. Hallyn" <serue@xxxxxxxxxx>
Cc: Paul Menage <menage@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/cgroup_freezer.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff -puN kernel/cgroup_freezer.c~freezer_cg-remove-task_lock-from-freezer_fork kernel/cgroup_freezer.c
--- a/kernel/cgroup_freezer.c~freezer_cg-remove-task_lock-from-freezer_fork
+++ a/kernel/cgroup_freezer.c
@@ -184,9 +184,13 @@ static void freezer_fork(struct cgroup_s
{
struct freezer *freezer;
- task_lock(task);
+ /*
+ * No lock is needed, since the task isn't on tasklist yet,
+ * so it can't be moved to another cgroup, which means the
+ * freezer won't be removed and will be valid during this
+ * function call.
+ */
freezer = task_freezer(task);
- task_unlock(task);
spin_lock_irq(&freezer->lock);
BUG_ON(freezer->state == CGROUP_FROZEN);
_
Patches currently in -mm which might be from lizf@xxxxxxxxxxxxxx are
cgroups-fix-invalid-cgrp-dentry-before-cgroup-has-been-completely-removed.patch
documentation-kernel-parameterstxt-update-isolcpus-kernel-option.patch
freezer_cg-remove-task_lock-from-freezer_fork.patch
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