Home » Mailing lists » Devel » [BUG]: Crash with CONFIG_FAIR_CGROUP_SCHED=y
[BUG]: Crash with CONFIG_FAIR_CGROUP_SCHED=y [message #22978] |
Thu, 08 November 2007 23:48 ![Go to next message Go to next message](/theme/ovz3/images/down.png) |
Sukadev Bhattiprolu
Messages: 413 Registered: August 2006
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Senior Member |
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With CONFIG_FAIR_CGROUP_SCHED=y, following commands on 2.6.24-rc1 crash
the system.
$ mount -t cgroup none /cgroups
$ ./ns_exec -cm /bin/ls
"ns_exec -cm" calls clone() to clone the mount namespace and then
executes the '/bin/ls' program in the cloned child.
Some observations that Serge and I made (we have been able to reproduce
reliably, but crash logs have not been very useful)
a. If we skip the 'mount' command, there is no crash.
b. If CONFIG_FAIR_CGROUP_SCHED=n again, there is no crash (even with
'mount' command).
c. mounting just the cpu or just the ns subsystem does not
lead to a crash. You can even
mount -t cgroup -o cpu none /mnt1
mount -t cgroup -o ns none /mnt2
and you still don't get a crash
d. mount -t cgroup -o cpu,ns none /cgroup
will always cause a crash with subsequent ns_exec
ns_exec.c and config file are attached. Let us know if you need more info.
Suka
---
Crash log:
Red Hat Enterprise Linux release 4.90 (Tikanga)
Kernel 2.6.24-rc1 on an x86_64
elm3a241 login: Unable to handle kernel NULL pointer dereferenceUnable to handle kernel NULL pointer dereference at 0000000000000000 RIP:
at 0000000000000000 RIP:
[<0000000000000000>]
[<0000000000000000>]
PGD 102d4d067 PGD 102d4d067 PUD 102c88067 PUD 102c88067 PMD 0 PMD 0
Oops: 0000 [1] Oops: 0000 [1] SMP SMP
CPU 2 CPU 2
Modules linked in:Modules linked in:
Pid: 3273, comm: ns_exec Not tainted 2.6.24-rc1 #9
Pid: 3273, comm: ns_exec Not tainted 2.6.24-rc1 #9
RIP: 0010:[<0000000000000000>] RIP: 0010:[<0000000000000000>] [<0000000000000000>]
[<0000000000000000>]
RSP: 0018:ffff8101006a6af0 EFLAGS: 00055292
RSP: 0018:ffff8101006a6af0 EFLAGS: 00055292
RAX: 0000000000000000 RBX: ffff810100d11140 RCX: ffff810101de4000
RAX: 0000000000000000 RBX: ffff810100d11140 RCX: ffff810101de4000
RDX: 0000000000000000 RSI: ffff810100d1a880 RDI: ffff810001037c00
RDX: 0000000000000000 RSI: ffff810100d1a880 RDI: ffff810001037c00
RBP: ffff810102c136c0 R08: ffff810101de4000 R09: ffff810101d31bb8
RBP: ffff810102c136c0 R08: ffff810101de4000 R09: ffff810101d31bb8
R10: 0000000000000000 R11: 00000000ffffffff R12: ffff8101034075b8
R10: 0000000000000000 R11: 00000000ffffffff R12: ffff8101034075b8
R13: ffff8101029d6028 R14: ffff810103407500 R15: ffffffff80869d00
R13: ffff8101029d6028 R14: ffff810103407500 R15: ffffffff80869d00
FS: 00002b80c2a396f0(0000) GS:ffff81010068f3c0(0000) knlGS:0000000000000000
FS: 00002b80c2a396f0(0000) GS:ffff81010068f3c0(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: 0000000000000000 CR3: 00000001028be000 CR4: 00000000000006e0
CR2: 0000000000000000 CR3: 00000001028be000 CR4: 00000000000006e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process ns_exec (pid: 3273, threadinfo ffff810101de4000, task ffff810100d11140)
Process ns_exec (pid: 3273, threadinfo ffff810101de4000, task ffff810100d11140)
Stack: Stack: 0000000000000000 0000000000000000 0000000000000001 0000000000000001 6c2f343662696c2f 6c2f343662696c2f 2d78756e696c2d64 2d78756e696c2d64
732e34362d363878 732e34362d363878 ffffffff00322e6f ffffffff00322e6f 762f003561736376 762f003561736376 0000357363762f63 0000357363762f63
0000000000000000 0000000000000000 0000000000000000 0000000000000000 762f73007665642f 762f73007665642f 0000317363762f63 0000317363762f63
Call Trace:
Call Trace:
Code: Code: Bad RIP value. Bad RIP value.
RIP RIP [<0000000000000000>]
[<0000000000000000>]
RSP <ffff8101006a6af0>
RSP <ffff8101006a6af0>
CR2: 0000000000000000
CR2: 0000000000000000
#
# Automatically generated make config: don't edit
# Linux kernel version: 2.6.24-rc1
# Thu Nov 8 13:38:29 2007
#
CONFIG_X86_64=y
CONFIG_64BIT=y
CONFIG_X86=y
CONFIG_GENERIC_TIME=y
CONFIG_GENERIC_TIME_VSYSCALL=y
CONFIG_GENERIC_CMOS_UPDATE=y
CONFIG_CLOCKSOURCE_WATCHDOG=y
CONFIG_GENERIC_CLOCKEVENTS=y
CONFIG_GENERIC_CLOCKEVENTS_BROADCAST=y
CONFIG_ZONE_DMA32=y
CONFIG_LOCKDEP_SUPPORT=y
CONFIG_STACKTRACE_SUPPORT=y
CONFIG_SEMAPHORE_SLEEPERS=y
CONFIG_MMU=y
CONFIG_ZONE_DMA=y
CONFIG_RWSEM_GENERIC_SPINLOCK=y
CONFIG_GENERIC_HWEIGHT=y
CONFIG_GENERIC_CALIBRATE_DELAY=y
CONFIG_X86_CMPXCHG=y
CONFIG_EARLY_PRINTK=y
CONFIG_GENERIC_ISA_DMA=y
CONFIG_GENERIC_IOMAP=y
CONFIG_ARCH_MAY_HAVE_PC_FDC=y
CONFIG_ARCH_POPULATES_NODE_MAP=y
CONFIG_DMI=y
CONFIG_AUDIT_ARCH=y
CONFIG_GENERIC_BUG=y
# CONFIG_ARCH_HAS_ILOG2_U32 is not set
# CONFIG_ARCH_HAS_ILOG2_U64 is not set
CONFIG_DEFCONFIG_LIST="/lib/modules/$UNAME_RELEASE/.config"
#
# General setup
#
CONFIG_EXPERIMENTAL=y
CONFIG_LOCK_KERNEL=y
CONFIG_INIT_ENV_ARG_LIMIT=32
CONFIG_LOCALVERSION=""
CONFIG_LOCALVERSION_AUTO=y
CONFIG_SWAP=y
CONFIG_SYSVIPC=y
CONFIG_SYSVIPC_SYSCTL=y
CONFIG_POSIX_MQUEUE=y
# CONFIG_BSD_PROCESS_ACCT is not set
# CONFIG_TASKSTATS is not set
CONFIG_USER_NS=y
# CONFIG_AUDIT is not set
CONFIG_IKCONFIG=y
CONFIG_IKCONFIG_PROC=y
CONFIG_LOG_BUF_SHIFT=18
CONFIG_CGROUPS=y
# CONFIG_CGROUP_DEBUG is not set
CONFIG_CGROUP_NS=y
# CONFIG_CGROUP_CPUACCT is not set
# CONFIG_CPUSETS is not set
CONFIG_FAIR_GROUP_SCHED=y
# CONFIG_FAIR_USER_SCHED is not set
CONFIG_FAIR_CGROUP_SCHED=y
CONFIG_SYSFS_DEPRECATED=y
CONFIG_RELAY=y
CONFIG_BLK_DEV_INITRD=y
CONFIG_INITRAMFS_SOURCE=""
CONFIG_CC_OPTIMIZE_FOR_SIZE=y
CONFIG_SYSCTL=y
# CONFIG_EMBEDDED is not set
CONFIG_UID16=y
CONFIG_SYSCTL_SYSCALL=y
CONFIG_KALLSYMS=y
CONFIG_KALLSYMS_ALL=y
# CONFIG_KALLSYMS_EXTRA_PASS is not set
CONFIG_HOTPLUG=y
CONFIG_PRINTK=y
CONFIG_BUG=y
CONFIG_ELF_CORE=y
CONFIG_BASE_FULL=y
CONFIG_FUTEX=y
CONFIG_ANON_INODES=y
CONFIG_EPOLL=y
CONFIG_SIGNALFD=y
CONFIG_EVENTFD=y
CONFIG_SHMEM=y
CONFIG_VM_EVENT_COUNTERS=y
CONFIG_SLAB=y
# CONFIG_SLUB is not set
# CONFIG_SLOB is not set
CONFIG_RT_MUTEXES=y
# CONFIG_TINY_SHMEM is not set
CONFIG_BASE_SMALL=0
CONFIG_MODULES=y
CONFIG_MODULE_UNLOAD=y
CONFIG_MODULE_FORCE_UNLOAD=y
# CONFIG_MODVERSIONS is not set
# CONFIG_MODULE_SRCVERSION_ALL is not set
# CONFIG_KMOD is not set
CONFIG_STOP_MACHINE=y
CONFIG_BLOCK=y
# CONFIG_BLK_DEV_IO_TRACE is not set
# CONFIG_BLK_DEV_BSG is not set
CONFIG_BLOCK_COMPAT=y
#
# IO Schedulers
#
CONFIG_IOSCHED_NOOP=y
# CONFIG_IOSCHED_AS is not set
CONFIG_IOSCHED_DEADLINE=y
CONFIG_IOSCHED_CFQ=y
# CONFIG_DEFAULT_AS is not set
# CONFIG_DEFAULT_DEADLINE is not set
CONFIG_DEFAULT_CFQ=y
# CONFIG_DEFAULT_NOOP is not set
CONFIG_DEFAULT_IOSCHED="cfq"
#
# Processor type and features
#
# CONFIG_TICK_ONESHOT is not set
# CONFIG_NO_HZ is not set
# CONFIG_HIGH_RES_TIMERS is not set
CONFIG_GENERIC_CLOCKEVENTS_BUILD=y
CONFIG_X86_PC=y
# CONFIG_X86_VSMP is not set
# CONFIG_MK8 is not set
# CONFIG_MPSC is not set
# CONFIG_MCORE2 is not set
CONFIG_GENERIC_CPU=y
CONFIG_X86_L1_CACHE_BYTES=128
CONFIG_X86_L1_CACHE_SHIFT=7
CONFIG_X86_INTERNODE_CACHE_BYTES=128
CONFIG_X86_TSC=y
CONFIG_X86_GOOD_APIC=y
# CONFIG_MICROCODE is not set
CONFIG_X86_MSR=y
CONFIG_X86_CPUID=y
CONFIG_X86_HT=y
CONFIG_X86_IO_APIC=y
CONFIG_X86_LOCAL_APIC=y
CONFIG_MTRR=y
CONFIG_SMP=y
CONFIG_SCHED_SMT=y
CONFIG_SCHED_MC=y
# CONFIG_PREEMPT_NONE is not set
CONFIG_PREEMPT_VOLUNTARY=y
# CONFIG_PREEMPT is not set
CONFIG_PREEMPT_BKL=y
CONFIG_NUMA=y
CONFIG_K8_NUMA=y
CONFIG_NODES_SHIFT=6
CONFIG_X86_64_ACPI_NUMA=y
CONFIG_NUMA_EMU=y
CONFIG_ARCH_DISCONTIGMEM_ENABLE=y
CONFIG_ARCH_DISCONTIGMEM_DEFAULT=y
CONFIG_ARCH_SPARSEMEM_ENABLE=y
CONFIG_SELECT_MEMORY_MODEL=y
# CONFIG_FLATMEM_MANUAL is not set
CONFIG_DISCONTIGMEM_MANUAL=y
# CONFIG_SPARSEMEM_MANUAL is not set
CONFIG_DISCONTIGMEM=y
CONFIG_FLAT_NODE_MEM_MAP=y
CONFIG_NEED_MULTIPLE_NODES=y
# CONFIG_SPARSEMEM_STATIC is not set
CONFIG_SPARSEMEM_VMEMMAP_ENABLE=y
CONFIG_SPLIT_PTLOCK_CPUS=4
CONFIG_MIGRATION=y
CONFIG_RESOURCES_64BIT=y
CONFIG_ZONE_DMA_FLAG=1
CONFIG_BOUNCE=y
CONFIG_VIRT_TO_BUS=y
CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID=y
CONFIG_OUT_OF_LINE_PFN_TO_PAGE=y
CONFIG_NR_CPUS=32
CONFIG_PHYSICAL_ALIGN=0x200000
CONFIG_HOTPLUG_CPU=y
CONFIG_ARCH_ENABLE_MEMORY_HOTPLUG=y
CONFIG_HPET_TIMER=y
CONFIG_HPET_EMULATE_RTC=y
CONFIG_IOMMU=y
# CONFIG_CALGARY_IOMMU is not set
CONFIG_SWIOTLB=y
CONFIG_X86_MCE=y
CONFIG_X86_MCE_INTEL=y
CONFIG_X86_MCE_AMD=y
# CONFIG_KEXEC is not set
# CONFIG_CRASH_DUMP is not set
# CONFIG_RELOCATABLE is not set
CONFIG_PHYSICAL_START=0x200000
CONFIG_SECCOMP=y
# CONFIG_CC_STACKPROTECTOR is not set
# CONFIG_HZ_100 is not set
CONFIG_HZ_250=y
# CONFIG_HZ_300 is not set
# CONFIG_HZ_1000 is not set
CONFIG_HZ=250
CONFIG_K8_NB=y
CONFIG_GENERIC_HARDIRQS=y
CONFIG_GENERIC_IRQ_PROBE=y
CONFIG_ISA_DMA_API=y
CONFIG_GENERIC_PENDING_IRQ=y
#
# Power management options
#
CONFIG_PM=y
# CONFIG_PM_LEGACY is not set
# CONFIG_PM_DEBUG is not set
CONFIG_PM_SLEEP_SMP=y
CONFIG_PM_SLEEP=y
CONFIG_SUSPEND_SMP_POSSIBLE=y
CONFIG_SUSPEND=y
CONFIG_HIBERNATION_SMP_POSSIBLE=y
CONFIG_HIBERNATION=y
CONFIG_PM_STD_PARTITION=""
CONFIG_ARCH_HIBERNATION_HEADER=y
CONFIG_ACPI=y
CONFIG_ACPI_SLEEP=y
CONFIG_ACPI_PROCFS=y
CONFIG_ACPI_PROC_EVENT=y
CONFIG_ACPI_BUTTON=y
CONFIG_ACPI_FAN=y
# CONFIG_ACPI_DOCK is not set
CONFIG_ACPI_PROCESSOR=y
CONFIG_ACPI_HOTPLUG_CPU=y
CONFIG_ACPI_THERMAL=y
CONFIG_ACPI_NUMA=y
# CONFIG_ACPI_ASUS is not set
# CONFIG_ACPI_TOSHIBA is not set
CONFIG_ACPI_BLACKLIST_YEAR=0
# CONFIG_ACPI_DEBUG is not set
CONFIG_ACPI_EC=y
CONFIG_ACPI_POWER=y
CONFIG_ACPI_SYSTEM=y
CONFIG_X86_PM_TIMER=y
CONFIG_ACPI_CONTAINER=y
#
# CPU Frequency scaling
#
CONFIG_CPU_FREQ=y
CONFIG_CPU_FREQ_TABLE=y
CONFIG_CPU_FREQ_DEBUG=y
CONFIG_CPU_FREQ_STAT=y
# CONFIG_CPU_FREQ_STAT_DETAILS is not set
CONFIG_CPU_FREQ_DEFAULT_GOV_PERFORMANCE=y
# CONFIG_CPU_FREQ_DEFAULT_GOV_USERSPACE is not set
# CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND is not set
# CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE is not set
CONFIG_CPU_FREQ_GOV_PERFORMANCE=y
# CONFIG_CPU_FREQ_GOV_POWERSAVE is not
...
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Re: [BUG]: Crash with CONFIG_FAIR_CGROUP_SCHED=y [message #22979 is a reply to message #22978] |
Fri, 09 November 2007 06:52 ![Go to previous message Go to previous message](/theme/ovz3/images/up.png) ![Go to next message Go to next message](/theme/ovz3/images/down.png) |
Srivatsa Vaddagiri
Messages: 241 Registered: August 2006
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Senior Member |
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On Thu, Nov 08, 2007 at 03:48:05PM -0800, sukadev@us.ibm.com wrote:
> With CONFIG_FAIR_CGROUP_SCHED=y, following commands on 2.6.24-rc1 crash
> the system.
Thanks for reporting the problem. It was caused because of the fact that
current task isn't kept in its runqueue in case of sched_fair class
tasks.
With the patch below, I could run ns_exec w/o any crash. Can you pls
verify it works for you as well?
Ingo,
Once Suka verifies that the patch fixes his crash, I would request you
to include the same in your tree and route it to Linus.
--
current task is not present in its runqueue in case of sched_fair class
tasks. Take care of this fact in rt_mutex_setprio(),
sched_setscheduler() and sched_move_task() routines.
Signed-off-by : Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
---
kernel/sched.c | 45 +++++++++++++++++++++++++--------------------
1 files changed, 25 insertions(+), 20 deletions(-)
Index: current/kernel/sched.c
===================================================================
--- current.orig/kernel/sched.c
+++ current/kernel/sched.c
@@ -3986,11 +3986,13 @@ void rt_mutex_setprio(struct task_struct
oldprio = p->prio;
on_rq = p->se.on_rq;
running = task_running(rq, p);
- if (on_rq) {
+ if (on_rq)
dequeue_task(rq, p, 0);
- if (running)
- p->sched_class->put_prev_task(rq, p);
- }
+ /* current task is not kept in its runqueue in case of sched_fair class.
+ * Hence we need the 'on_rq?' and 'running?' tests to be separate.
+ */
+ if (running)
+ p->sched_class->put_prev_task(rq, p);
if (rt_prio(prio))
p->sched_class = &rt_sched_class;
@@ -3999,9 +4001,9 @@ void rt_mutex_setprio(struct task_struct
p->prio = prio;
+ if (running)
+ p->sched_class->set_curr_task(rq);
if (on_rq) {
- if (running)
- p->sched_class->set_curr_task(rq);
enqueue_task(rq, p, 0);
inc_load(rq, p);
/*
@@ -4298,18 +4300,20 @@ recheck:
update_rq_clock(rq);
on_rq = p->se.on_rq;
running = task_running(rq, p);
- if (on_rq) {
+ if (on_rq)
deactivate_task(rq, p, 0);
- if (running)
- p->sched_class->put_prev_task(rq, p);
- }
+ /* current task is not kept in its runqueue in case of sched_fair class.
+ * Hence we need the 'on_rq?' and 'running?' tests to be separate.
+ */
+ if (running)
+ p->sched_class->put_prev_task(rq, p);
oldprio = p->prio;
__setscheduler(rq, p, policy, param->sched_priority);
+ if (running)
+ p->sched_class->set_curr_task(rq);
if (on_rq) {
- if (running)
- p->sched_class->set_curr_task(rq);
activate_task(rq, p, 0);
/*
* Reschedule if we are currently running on this runqueue and
@@ -7036,19 +7040,20 @@ void sched_move_task(struct task_struct
running = task_running(rq, tsk);
on_rq = tsk->se.on_rq;
- if (on_rq) {
+ if (on_rq)
dequeue_task(rq, tsk, 0);
- if (unlikely(running))
- tsk->sched_class->put_prev_task(rq, tsk);
- }
+ /* current task is not kept in its runqueue in case of sched_fair class.
+ * Hence we need the 'on_rq?' and 'running?' tests to be separate.
+ */
+ if (unlikely(running))
+ tsk->sched_class->put_prev_task(rq, tsk);
set_task_cfs_rq(tsk);
- if (on_rq) {
- if (unlikely(running))
- tsk->sched_class->set_curr_task(rq);
+ if (unlikely(running))
+ tsk->sched_class->set_curr_task(rq);
+ if (on_rq)
enqueue_task(rq, tsk, 0);
- }
done:
task_rq_unlock(rq, &flags);
--
Regards,
vatsa
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Re: [BUG]: Crash with CONFIG_FAIR_CGROUP_SCHED=y [message #22991 is a reply to message #22979] |
Fri, 09 November 2007 08:45 ![Go to previous message Go to previous message](/theme/ovz3/images/up.png) ![Go to next message Go to next message](/theme/ovz3/images/down.png) |
Dmitry Adamushko
Messages: 20 Registered: June 2007
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Junior Member |
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Hi Srivatsa,
> [ ... ]
> --
>
> current task is not present in its runqueue in case of sched_fair class
> tasks. Take care of this fact in rt_mutex_setprio(),
> sched_setscheduler() and sched_move_task() routines.
>
> Signed-off-by : Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
>
>
> ---
> kernel/sched.c | 45 +++++++++++++++++++++++++--------------------
> 1 files changed, 25 insertions(+), 20 deletions(-)
>
> Index: current/kernel/sched.c
> ===================================================================
> --- current.orig/kernel/sched.c
> +++ current/kernel/sched.c
> @@ -3986,11 +3986,13 @@ void rt_mutex_setprio(struct task_struct
> oldprio = p->prio;
> on_rq = p->se.on_rq;
> running = task_running(rq, p);
> - if (on_rq) {
> + if (on_rq)
> dequeue_task(rq, p, 0);
> - if (running)
> - p->sched_class->put_prev_task(rq, p);
> - }
> + /* current task is not kept in its runqueue in case of sched_fair class.
> + * Hence we need the 'on_rq?' and 'running?' tests to be separate.
Humm... the 'current' is not kept within the tree but
current->se.on_rq is supposed to be '1' ,
so the old code looks ok to me (at least for the 'leaf' elements).
Maybe you were able to get more useful oops on your site?
> --
> Regards,
> vatsa
>
--
Best regards,
Dmitry Adamushko
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Re: [BUG]: Crash with CONFIG_FAIR_CGROUP_SCHED=y [message #22997 is a reply to message #22991] |
Fri, 09 November 2007 10:04 ![Go to previous message Go to previous message](/theme/ovz3/images/up.png) ![Go to next message Go to next message](/theme/ovz3/images/down.png) |
Srivatsa Vaddagiri
Messages: 241 Registered: August 2006
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Senior Member |
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On Fri, Nov 09, 2007 at 09:45:21AM +0100, Dmitry Adamushko wrote:
> Humm... the 'current' is not kept within the tree but
> current->se.on_rq is supposed to be '1' ,
> so the old code looks ok to me (at least for the 'leaf' elements).
You are damned right! Sorry my mistake with the previous analysis and
(as I now find out) testing :(
There are couple of problems discovered by Suka's test:
- The test requires the cgroup filesystem to be mounted with
atleast the cpu and ns options (i.e both namespace and cpu
controllers are active in the same hierarchy).
# mkdir /dev/cpuctl
# mount -t cgroup -ocpu,ns none cpuctl
(or simply)
# mount -t cgroup none cpuctl -> Will activate all controllers
in same hierarchy.
- The test invokes clone() with CLONE_NEWNS set. This causes a a new child
to be created, also a new group (do_fork->copy_namespaces->ns_cgroup_clone->
cgroup_clone) and the child is attached to the new group (cgroup_clone->
attach_task->sched_move_task). At this point in time, the child's scheduler
related fields are uninitialized (including its on_rq field, which it has
inherited from parent). As a result sched_move_task thinks its on
runqueue, when it isn't.
As a solution to this problem, I moved sched_fork() call, which
initializes scheduler related fields on a new task, before
copy_namespaces(). I am not sure though whether moving up will
cause other side-effects. Do you see any issue?
- The second problem exposed by this test is that task_new_fair()
assumes that parent and child will be part of the same group (which
needn't be as this test shows). As a result, cfs_rq->curr can be NULL
for the child.
The solution is to test for curr pointer being NULL in
task_new_fair().
With the patch below, I could run ns_exec() fine w/o a crash.
Suka, can you verify whether this patch fixes your problem?
--
Fix copy_namespace() <-> sched_fork() dependency in do_fork, by moving
up sched_fork().
Also introduce a NULL pointer check for 'curr' in task_new_fair().
Signed-off-by : Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
---
kernel/fork.c | 6 +++---
kernel/sched_fair.c | 2 +-
2 files changed, 4 insertions(+), 4 deletions(-)
Index: current/kernel/fork.c
===================================================================
--- current.orig/kernel/fork.c
+++ current/kernel/fork.c
@@ -1121,6 +1121,9 @@ static struct task_struct *copy_process(
p->blocked_on = NULL; /* not blocked yet */
#endif
+ /* Perform scheduler related setup. Assign this task to a CPU. */
+ sched_fork(p, clone_flags);
+
if ((retval = security_task_alloc(p)))
goto bad_fork_cleanup_policy;
if ((retval = audit_alloc(p)))
@@ -1210,9 +1213,6 @@ static struct task_struct *copy_process(
INIT_LIST_HEAD(&p->ptrace_children);
INIT_LIST_HEAD(&p->ptrace_list);
- /* Perform scheduler related setup. Assign this task to a CPU. */
- sched_fork(p, clone_flags);
-
/* Now that the task is set up, run cgroup callbacks if
* necessary. We need to run them before the task is visible
* on the tasklist. */
Index: current/kernel/sched_fair.c
===================================================================
--- current.orig/kernel/sched_fair.c
+++ current/kernel/sched_fair.c
@@ -1023,7 +1023,7 @@ static void task_new_fair(struct rq *rq,
place_entity(cfs_rq, se, 1);
if (sysctl_sched_child_runs_first && this_cpu == task_cpu(p) &&
- curr->vruntime < se->vruntime) {
+ curr && curr->vruntime < se->vruntime) {
/*
* Upon rescheduling, sched_class::put_prev_task() will place
* 'current' within the tree based on its new key value.
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Re: [BUG]: Crash with CONFIG_FAIR_CGROUP_SCHED=y [message #23001 is a reply to message #22997] |
Fri, 09 November 2007 10:59 ![Go to previous message Go to previous message](/theme/ovz3/images/up.png) ![Go to next message Go to next message](/theme/ovz3/images/down.png) |
Dmitry Adamushko
Messages: 20 Registered: June 2007
|
Junior Member |
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On 09/11/2007, Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com> wrote:
> [ ... ]
>
> As a solution to this problem, I moved sched_fork() call, which
> initializes scheduler related fields on a new task, before
> copy_namespaces(). I am not sure though whether moving up will
> cause other side-effects. Do you see any issue?
Should be ok (IMHO and at first glance :-)
> - The second problem exposed by this test is that task_new_fair()
> assumes that parent and child will be part of the same group (which
> needn't be as this test shows). As a result, cfs_rq->curr can be NULL
> for the child.
Would it be better, logically-wise, to use is_same_group() instead?
Although, we can't have 2 groups with cfs_rq->curr != NULL on the same
CPU... so if the child belongs to another group, it's cfs_rq->curr is
automatically NULL indeed.
--
Best regards,
Dmitry Adamushko
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Re: [BUG]: Crash with CONFIG_FAIR_CGROUP_SCHED=y [message #23006 is a reply to message #23001] |
Fri, 09 November 2007 12:01 ![Go to previous message Go to previous message](/theme/ovz3/images/up.png) ![Go to next message Go to next message](/theme/ovz3/images/down.png) |
Srivatsa Vaddagiri
Messages: 241 Registered: August 2006
|
Senior Member |
|
|
On Fri, Nov 09, 2007 at 11:59:15AM +0100, Dmitry Adamushko wrote:
> > - The second problem exposed by this test is that task_new_fair()
> > assumes that parent and child will be part of the same group (which
> > needn't be as this test shows). As a result, cfs_rq->curr can be NULL
> > for the child.
>
> Would it be better, logically-wise, to use is_same_group() instead?
> Although, we can't have 2 groups with cfs_rq->curr != NULL on the same
> CPU... so if the child belongs to another group, it's cfs_rq->curr is
> automatically NULL indeed.
Yeah ..I feel safe with an explicit !curr check, perhaps with a comment like
below added to explain when curr can be NULL?
---
kernel/sched_fair.c | 1 +
1 files changed, 1 insertion(+)
Index: current/kernel/sched_fair.c
===================================================================
--- current.orig/kernel/sched_fair.c
+++ current/kernel/sched_fair.c
@@ -1022,6 +1022,7 @@ static void task_new_fair(struct rq *rq,
update_curr(cfs_rq);
place_entity(cfs_rq, se, 1);
+ /* 'curr' will be NULL if the child belongs to a different group */
if (sysctl_sched_child_runs_first && this_cpu == task_cpu(p) &&
curr && curr->vruntime < se->vruntime) {
/*
--
Regards,
vatsa
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Re: [BUG]: Crash with CONFIG_FAIR_CGROUP_SCHED=y [message #23022 is a reply to message #22997] |
Fri, 09 November 2007 16:05 ![Go to previous message Go to previous message](/theme/ovz3/images/up.png) ![Go to next message Go to next message](/theme/ovz3/images/down.png) |
serue
Messages: 750 Registered: February 2006
|
Senior Member |
|
|
Quoting Srivatsa Vaddagiri (vatsa@linux.vnet.ibm.com):
> On Fri, Nov 09, 2007 at 09:45:21AM +0100, Dmitry Adamushko wrote:
> > Humm... the 'current' is not kept within the tree but
> > current->se.on_rq is supposed to be '1' ,
> > so the old code looks ok to me (at least for the 'leaf' elements).
>
> You are damned right! Sorry my mistake with the previous analysis and
> (as I now find out) testing :(
>
> There are couple of problems discovered by Suka's test:
>
> - The test requires the cgroup filesystem to be mounted with
> atleast the cpu and ns options (i.e both namespace and cpu
> controllers are active in the same hierarchy).
>
> # mkdir /dev/cpuctl
> # mount -t cgroup -ocpu,ns none cpuctl
> (or simply)
> # mount -t cgroup none cpuctl -> Will activate all controllers
> in same hierarchy.
>
> - The test invokes clone() with CLONE_NEWNS set. This causes a a new child
> to be created, also a new group (do_fork->copy_namespaces->ns_cgroup_clone->
> cgroup_clone) and the child is attached to the new group (cgroup_clone->
> attach_task->sched_move_task). At this point in time, the child's scheduler
> related fields are uninitialized (including its on_rq field, which it has
> inherited from parent). As a result sched_move_task thinks its on
> runqueue, when it isn't.
>
> As a solution to this problem, I moved sched_fork() call, which
> initializes scheduler related fields on a new task, before
> copy_namespaces(). I am not sure though whether moving up will
> cause other side-effects. Do you see any issue?
>
> - The second problem exposed by this test is that task_new_fair()
> assumes that parent and child will be part of the same group (which
> needn't be as this test shows). As a result, cfs_rq->curr can be NULL
> for the child.
>
> The solution is to test for curr pointer being NULL in
> task_new_fair().
>
>
> With the patch below, I could run ns_exec() fine w/o a crash.
>
> Suka, can you verify whether this patch fixes your problem?
Works on my machine. Thanks!
> --
>
> Fix copy_namespace() <-> sched_fork() dependency in do_fork, by moving
> up sched_fork().
>
> Also introduce a NULL pointer check for 'curr' in task_new_fair().
>
> Signed-off-by : Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Tested-by: Serge Hallyn <serue@us.ibm.com>
>
> ---
> kernel/fork.c | 6 +++---
> kernel/sched_fair.c | 2 +-
> 2 files changed, 4 insertions(+), 4 deletions(-)
>
> Index: current/kernel/fork.c
> ===================================================================
> --- current.orig/kernel/fork.c
> +++ current/kernel/fork.c
> @@ -1121,6 +1121,9 @@ static struct task_struct *copy_process(
> p->blocked_on = NULL; /* not blocked yet */
> #endif
>
> + /* Perform scheduler related setup. Assign this task to a CPU. */
> + sched_fork(p, clone_flags);
> +
> if ((retval = security_task_alloc(p)))
> goto bad_fork_cleanup_policy;
> if ((retval = audit_alloc(p)))
> @@ -1210,9 +1213,6 @@ static struct task_struct *copy_process(
> INIT_LIST_HEAD(&p->ptrace_children);
> INIT_LIST_HEAD(&p->ptrace_list);
>
> - /* Perform scheduler related setup. Assign this task to a CPU. */
> - sched_fork(p, clone_flags);
> -
> /* Now that the task is set up, run cgroup callbacks if
> * necessary. We need to run them before the task is visible
> * on the tasklist. */
> Index: current/kernel/sched_fair.c
> ===================================================================
> --- current.orig/kernel/sched_fair.c
> +++ current/kernel/sched_fair.c
> @@ -1023,7 +1023,7 @@ static void task_new_fair(struct rq *rq,
> place_entity(cfs_rq, se, 1);
>
> if (sysctl_sched_child_runs_first && this_cpu == task_cpu(p) &&
> - curr->vruntime < se->vruntime) {
> + curr && curr->vruntime < se->vruntime) {
> /*
> * Upon rescheduling, sched_class::put_prev_task() will place
> * 'current' within the tree based on its new key value.
> _______________________________________________
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> Containers@lists.linux-foundation.org
> https://lists.linux-foundation.org/mailman/listinfo/containers
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Re: [BUG]: Crash with CONFIG_FAIR_CGROUP_SCHED=y [message #23039 is a reply to message #23022] |
Sat, 10 November 2007 23:13 ![Go to previous message Go to previous message](/theme/ovz3/images/up.png) |
Sukadev Bhattiprolu
Messages: 413 Registered: August 2006
|
Senior Member |
|
|
Serge E. Hallyn [serue@us.ibm.com] wrote:
| Quoting Srivatsa Vaddagiri (vatsa@linux.vnet.ibm.com):
| > On Fri, Nov 09, 2007 at 09:45:21AM +0100, Dmitry Adamushko wrote:
| > > Humm... the 'current' is not kept within the tree but
| > > current->se.on_rq is supposed to be '1' ,
| > > so the old code looks ok to me (at least for the 'leaf' elements).
| >
| > You are damned right! Sorry my mistake with the previous analysis and
| > (as I now find out) testing :(
| >
| > There are couple of problems discovered by Suka's test:
| >
| > - The test requires the cgroup filesystem to be mounted with
| > atleast the cpu and ns options (i.e both namespace and cpu
| > controllers are active in the same hierarchy).
| >
| > # mkdir /dev/cpuctl
| > # mount -t cgroup -ocpu,ns none cpuctl
| > (or simply)
| > # mount -t cgroup none cpuctl -> Will activate all controllers
| > in same hierarchy.
| >
| > - The test invokes clone() with CLONE_NEWNS set. This causes a a new child
| > to be created, also a new group (do_fork->copy_namespaces->ns_cgroup_clone->
| > cgroup_clone) and the child is attached to the new group (cgroup_clone->
| > attach_task->sched_move_task). At this point in time, the child's scheduler
| > related fields are uninitialized (including its on_rq field, which it has
| > inherited from parent). As a result sched_move_task thinks its on
| > runqueue, when it isn't.
| >
| > As a solution to this problem, I moved sched_fork() call, which
| > initializes scheduler related fields on a new task, before
| > copy_namespaces(). I am not sure though whether moving up will
| > cause other side-effects. Do you see any issue?
| >
| > - The second problem exposed by this test is that task_new_fair()
| > assumes that parent and child will be part of the same group (which
| > needn't be as this test shows). As a result, cfs_rq->curr can be NULL
| > for the child.
| >
| > The solution is to test for curr pointer being NULL in
| > task_new_fair().
| >
| >
| > With the patch below, I could run ns_exec() fine w/o a crash.
| >
| > Suka, can you verify whether this patch fixes your problem?
|
| Works on my machine. Thanks!
And mine too. Thanks,
|
| > --
| >
| > Fix copy_namespace() <-> sched_fork() dependency in do_fork, by moving
| > up sched_fork().
| >
| > Also introduce a NULL pointer check for 'curr' in task_new_fair().
| >
| > Signed-off-by : Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
|
| Tested-by: Serge Hallyn <serue@us.ibm.com>
Tested-by: Sukadev Bhattiprolu <sukadev@us.ibm.com>
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