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