a0c1e9073e
Not all architectures implement futex_atomic_cmpxchg_inatomic(). The default implementation returns -ENOSYS, which is currently not handled inside of the futex guts. Futex PI calls and robust list exits with a held futex result in an endless loop in the futex code on architectures which have no support. Fixing up every place where futex_atomic_cmpxchg_inatomic() is called would add a fair amount of extra if/else constructs to the already complex code. It is also not possible to disable the robust feature before user space tries to register robust lists. Compile time disabling is not a good idea either, as there are already architectures with runtime detection of futex_atomic_cmpxchg_inatomic support. Detect the functionality at runtime instead by calling cmpxchg_futex_value_locked() with a NULL pointer from the futex initialization code. This is guaranteed to fail, but the call of futex_atomic_cmpxchg_inatomic() happens with pagefaults disabled. On architectures, which use the asm-generic implementation or have a runtime CPU feature detection, a -ENOSYS return value disables the PI/robust features. On architectures with a working implementation the call returns -EFAULT and the PI/robust features are enabled. The relevant syscalls return -ENOSYS and the robust list exit code is blocked, when the detection fails. Fixes http://lkml.org/lkml/2008/2/11/149 Originally reported by: Lennart Buytenhek Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: Lennert Buytenhek <buytenh@wantstofly.org> Cc: Riku Voipio <riku.voipio@movial.fi> Cc: <stable@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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irq | ||
power | ||
time | ||
.gitignore | ||
acct.c | ||
audit_tree.c | ||
audit.c | ||
audit.h | ||
auditfilter.c | ||
auditsc.c | ||
backtracetest.c | ||
capability.c | ||
cgroup_debug.c | ||
cgroup.c | ||
compat.c | ||
configs.c | ||
cpu.c | ||
cpuset.c | ||
delayacct.c | ||
dma.c | ||
exec_domain.c | ||
exit.c | ||
extable.c | ||
fork.c | ||
futex_compat.c | ||
futex.c | ||
hrtimer.c | ||
itimer.c | ||
kallsyms.c | ||
Kconfig.hz | ||
Kconfig.preempt | ||
kexec.c | ||
kfifo.c | ||
kmod.c | ||
kprobes.c | ||
ksysfs.c | ||
kthread.c | ||
latencytop.c | ||
lockdep_internals.h | ||
lockdep_proc.c | ||
lockdep.c | ||
Makefile | ||
marker.c | ||
module.c | ||
mutex-debug.c | ||
mutex-debug.h | ||
mutex.c | ||
mutex.h | ||
notifier.c | ||
ns_cgroup.c | ||
nsproxy.c | ||
panic.c | ||
params.c | ||
pid_namespace.c | ||
pid.c | ||
pm_qos_params.c | ||
posix-cpu-timers.c | ||
posix-timers.c | ||
printk.c | ||
profile.c | ||
ptrace.c | ||
rcuclassic.c | ||
rcupdate.c | ||
rcupreempt_trace.c | ||
rcupreempt.c | ||
rcutorture.c | ||
relay.c | ||
res_counter.c | ||
resource.c | ||
rtmutex_common.h | ||
rtmutex-debug.c | ||
rtmutex-debug.h | ||
rtmutex-tester.c | ||
rtmutex.c | ||
rtmutex.h | ||
rwsem.c | ||
sched_debug.c | ||
sched_fair.c | ||
sched_idletask.c | ||
sched_rt.c | ||
sched_stats.h | ||
sched.c | ||
seccomp.c | ||
signal.c | ||
softirq.c | ||
softlockup.c | ||
spinlock.c | ||
srcu.c | ||
stacktrace.c | ||
stop_machine.c | ||
sys_ni.c | ||
sys.c | ||
sysctl_check.c | ||
sysctl.c | ||
taskstats.c | ||
test_kprobes.c | ||
time.c | ||
timeconst.pl | ||
timer.c | ||
tsacct.c | ||
uid16.c | ||
user_namespace.c | ||
user.c | ||
utsname_sysctl.c | ||
utsname.c | ||
wait.c | ||
workqueue.c |