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Message-ID: <20061201164632.GA26550@in.ibm.com>
Date: Fri, 1 Dec 2006 22:16:32 +0530
From: Srivatsa Vaddagiri <vatsa@...ibm.com>
To: menage@...gle.com
Cc: akpm@...l.org, pj@....com, sekharan@...ibm.com, dev@...ru,
xemul@...ru, ckrm-tech@...ts.sourceforge.net,
linux-kernel@...r.kernel.org, mbligh@...gle.com, winget@...gle.com,
rohitseth@...gle.com, devel@...nvz.org,
Ingo Molnar <mingo@...e.hu>,
Nick Piggin <nickpiggin@...oo.com.au>,
Dipankar <dipankar@...ibm.com>, Balbir Singh <balbir@...ibm.com>
Subject: [Patch 1/3] Miscellaneous container fixes
This patches fixes various bugs I hit in the recently posted container
patches.
1. If a subsystem registers with fork/exit hook during bootup (much
before rcu is initialized), then the resulting synchronize_rcu() in
container_register_subsys() hangs. Avoid this by not calling
synchronize_rcu() if we arent fully booted yet.
2. If cpuset_create fails() for some reason, then the resulting
call to cpuset_destroy can trip. Avoid this by initializing
container->...->cpuset pointer to NULL in cpuset_create().
3. container_rmdir->cpuset_destroy->update_flag can deadlock on
container_lock(). Avoid this by introducing __update_flag, which
doesnt take container_lock().
(I have also hit some lockdep warnings. Will post them after some
review, to make sure that they are not introduced by my patches).
Signed-off-by : Srivatsa Vaddagiri <vatsa@...ibm.com>
---
linux-2.6.19-rc6-vatsa/kernel/container.c | 4 ++-
linux-2.6.19-rc6-vatsa/kernel/cpuset.c | 35 ++++++++++++++++++++++++------
2 files changed, 31 insertions(+), 8 deletions(-)
diff -puN kernel/container.c~container_fixes kernel/container.c
--- linux-2.6.19-rc6/kernel/container.c~container_fixes 2006-12-01 16:19:41.000000000 +0530
+++ linux-2.6.19-rc6-vatsa/kernel/container.c 2006-12-01 16:20:20.000000000 +0530
@@ -1344,6 +1344,7 @@ static long container_create(struct cont
cont->parent = parent;
cont->root = parent->root;
cont->hierarchy = parent->hierarchy;
+ cont->top_container = parent->top_container;
for_each_subsys(cont->hierarchy, ss) {
err = ss->create(ss, cont);
@@ -1580,7 +1581,8 @@ int container_register_subsys(struct con
if (!need_forkexit_callback &&
(new_subsys->fork || new_subsys->exit)) {
need_forkexit_callback = 1;
- synchronize_rcu();
+ if (system_state == SYSTEM_RUNNING)
+ synchronize_rcu();
}
/* If this subsystem requested that it be notified with fork
diff -puN kernel/cpuset.c~container_fixes kernel/cpuset.c
--- linux-2.6.19-rc6/kernel/cpuset.c~container_fixes 2006-12-01 19:02:35.000000000 +0530
+++ linux-2.6.19-rc6-vatsa/kernel/cpuset.c 2006-12-01 20:43:52.000000000 +0530
@@ -97,14 +97,22 @@ struct cpuset {
/* Update the cpuset for a container */
static inline void set_container_cs(struct container *cont, struct cpuset *cs)
{
- cont->subsys[cpuset_subsys.subsys_id] = &cs->css;
+ if (cs)
+ cont->subsys[cpuset_subsys.subsys_id] = &cs->css;
+ else
+ cont->subsys[cpuset_subsys.subsys_id] = NULL;
}
/* Retrieve the cpuset for a container */
static inline struct cpuset *container_cs(struct container *cont)
{
- return container_of(container_subsys_state(cont, &cpuset_subsys),
- struct cpuset, css);
+ struct container_subsys_state *css;
+
+ css = container_subsys_state(cont, &cpuset_subsys);
+ if (css)
+ return container_of(css, struct cpuset, css);
+ else
+ return NULL;
}
/* Retrieve the cpuset for a task */
@@ -698,7 +706,7 @@ static int update_memory_pressure_enable
* Call with manage_mutex held.
*/
-static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs, char *buf)
+static int __update_flag(cpuset_flagbits_t bit, struct cpuset *cs, char *buf)
{
int turning_on;
struct cpuset trialcs;
@@ -717,18 +725,27 @@ static int update_flag(cpuset_flagbits_t
return err;
cpu_exclusive_changed =
(is_cpu_exclusive(cs) != is_cpu_exclusive(&trialcs));
- container_lock();
if (turning_on)
set_bit(bit, &cs->flags);
else
clear_bit(bit, &cs->flags);
- container_unlock();
if (cpu_exclusive_changed)
update_cpu_domains(cs);
return 0;
}
+static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs, char *buf)
+{
+ int err;
+
+ container_lock();
+ err = __update_flag(bit, cs, buf);
+ container_unlock();
+
+ return err;
+}
+
/*
* Frequency meter - How fast is some event occurring?
*
@@ -1165,6 +1182,7 @@ int cpuset_create(struct container_subsy
return 0;
}
parent = container_cs(cont->parent);
+ set_container_cs(cont, NULL);
cs = kmalloc(sizeof(*cs), GFP_KERNEL);
if (!cs)
return -ENOMEM;
@@ -1202,9 +1220,12 @@ void cpuset_destroy(struct container_sub
{
struct cpuset *cs = container_cs(cont);
+ if (!cs)
+ return;
+
cpuset_update_task_memory_state();
if (is_cpu_exclusive(cs)) {
- int retval = update_flag(CS_CPU_EXCLUSIVE, cs, "0");
+ int retval = __update_flag(CS_CPU_EXCLUSIVE, cs, "0");
BUG_ON(retval);
}
number_of_cpusets--;
_
--
Regards,
vatsa
-
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