[PATCH] Cpuset: remove test for null cpuset from alloc code path

[PATCH] Cpuset: remove test for null cpuset from alloc code path

Post by Paul Jacks » Tue, 13 Dec 2005 15:50:10


emove a couple of more lines of code from the cpuset hooks in
the page allocation code path.

There was a check for a NULL cpuset pointer in the routine
cpuset_update_task_memory_state() that was only needed during
system boot, after the memory subsystem was initialized,
before the cpuset subsystem was initialized, to catch a NULL
task->cpuset pointer.

Add a cpuset_init_early() routine, just before the mem_init()
call in init/main.c, that sets up just enough of the init tasks
cpuset structure to render cpuset_update_task_memory_state()
calls harmless.

Signed-off-by: Paul Jackson < XXXX@XXXXX.COM >

---

include/linux/cpuset.h | 2 ++
init/main.c | 1 +
kernel/cpuset.c | 22 ++++++++++++++++------
3 files changed, 19 insertions(+), 6 deletions(-)

--- 2.6.15-rc3-mm1.orig/include/linux/cpuset.h 2005-12-11 01:01:21.965124900 -0800
+++ 2.6.15-rc3-mm1/include/linux/cpuset.h 2005-12-11 21:16:38.207522306 -0800
@@ -16,6 +16,7 @@

extern int number_of_cpusets; /* How many cpusets are defined in system? */

+extern int cpuset_init_early(void);
extern int cpuset_init(void);
extern void cpuset_init_smp(void);
extern void cpuset_fork(struct task_struct *p);
@@ -49,6 +50,7 @@ extern char *cpuset_task_status_allowed(

#else /* !CONFIG_CPUSETS */

+static inline int cpuset_init_early(void) { return 0; }
static inline int cpuset_init(void) { return 0; }
static inline void cpuset_init_smp(void) {}
static inline void cpuset_fork(struct task_struct *p) {}
--- 2.6.15-rc3-mm1.orig/init/main.c 2005-12-07 15:45:00.720991835 -0800
+++ 2.6.15-rc3-mm1/init/main.c 2005-12-11 21:06:27.926145263 -0800
@@ -513,6 +513,7 @@ asmlinkage void __init start_kernel(void
}
#endif
vfs_caches_init_early();
+ cpuset_init_early();
mem_init();
kmem_cache_init();
setup_per_cpu_pageset();
--- 2.6.15-rc3-mm1.orig/kernel/cpuset.c 2005-12-11 14:30:08.374254561 -0800
+++ 2.6.15-rc3-mm1/kernel/cpuset.c 2005-12-11 22:35:39.051718313 -0800
@@ -619,9 +619,7 @@ static void guarantee_online_mems(const
* Do not call this routine if in_interrupt().
*
* Call without callback_sem or task_lock() held. May be called
- * with or without manage_sem held. Except in early boot or
- * an exiting task, when tsk->cpuset is NULL, this routine will
- * acquire task_lock(). We don't need to use task_lock to guard
+ * with or without manage_sem held. Doesn't need task_lock to guard
* against another task changing a non-NULL cpuset pointer to NULL,
* as that is only done by a task on itself, and if the current task
* is here, it is not simultaneously in the exit code NULL'ing its
@@ -646,9 +644,6 @@ void cpuset_update_task_memory_state()
struct task_struct *tsk = current;
struct cpuset *cs = tsk->cpuset;

- if (unlikely(!cs))
- return;
-
rcu_read_lock();
my_cpusets_mem_gen = cs->mems_generation;
rcu_read_unlock();
@@ -1851,6 +1846,21 @@ static int cpuset_rmdir(struct inode *un
return 0;
}

+/*
+ * cpuset_init_early - just enough so that the calls to
+ * cpuset_update_task_memory_state() in early init code
+ * are harmless.
+ */
+
+int __init cpuset_init_early(void)
+{
+ struct task_struct *tsk = current;
+
+ tsk->cpuset = &top_cpuset;
+ tsk->cpuset->mems_generation = atomic_read(&cpuset_mems_generation);
+ return 0;
+}
+
/**
* cpuset_init - initialize cpusets at system boot
*

--