linux-stable-rt/kernel
Ingo Molnar 86998aa653 [PATCH] genirq core: fix handle_level_irq()
while porting the -rt tree to 2.6.18-rc7 i noticed the following
screaming-IRQ scenario on an SMP system:

 2274  0Dn.:1 0.001ms: do_IRQ+0xc/0x103  <= (ret_from_intr+0x0/0xf)
 2274  0Dn.:1 0.010ms: do_IRQ+0xc/0x103  <= (ret_from_intr+0x0/0xf)
 2274  0Dn.:1 0.020ms: do_IRQ+0xc/0x103  <= (ret_from_intr+0x0/0xf)
 2274  0Dn.:1 0.029ms: do_IRQ+0xc/0x103  <= (ret_from_intr+0x0/0xf)
 2274  0Dn.:1 0.039ms: do_IRQ+0xc/0x103  <= (ret_from_intr+0x0/0xf)
 2274  0Dn.:1 0.048ms: do_IRQ+0xc/0x103  <= (ret_from_intr+0x0/0xf)
 2274  0Dn.:1 0.058ms: do_IRQ+0xc/0x103  <= (ret_from_intr+0x0/0xf)
 2274  0Dn.:1 0.068ms: do_IRQ+0xc/0x103  <= (ret_from_intr+0x0/0xf)
 2274  0Dn.:1 0.077ms: do_IRQ+0xc/0x103  <= (ret_from_intr+0x0/0xf)
 2274  0Dn.:1 0.087ms: do_IRQ+0xc/0x103  <= (ret_from_intr+0x0/0xf)
 2274  0Dn.:1 0.097ms: do_IRQ+0xc/0x103  <= (ret_from_intr+0x0/0xf)

as it turns out, the bug is caused by handle_level_irq(), which if it
races with another CPU already handling this IRQ, it _unmasks_ the IRQ
line on the way out. This is not how 2.6.17 works, and we introduced
this bug in one of the early genirq cleanups right before it went into
-mm. (the bug was not in the genirq patchset for a long time, and we
didnt notice the bug due to the lack of -rt rebase to the new genirq
code. -rt, and hardirq-preemption in particular opens up such races much
wider than anything else.)

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-09-19 07:57:20 -07:00
..
irq [PATCH] genirq core: fix handle_level_irq() 2006-09-19 07:57:20 -07:00
power [PATCH] prevent swsusp with PAE 2006-09-06 11:00:02 -07:00
time
.gitignore
Kconfig.hz
Kconfig.preempt
Makefile
acct.c
audit.c [PATCH] sanity check audit_buffer 2006-09-11 13:32:17 -04:00
audit.h [PATCH] audit: AUDIT_PERM support 2006-09-11 13:32:30 -04:00
auditfilter.c [PATCH] audit: AUDIT_PERM support 2006-09-11 13:32:30 -04:00
auditsc.c [PATCH] audit: AUDIT_PERM support 2006-09-11 13:32:30 -04:00
capability.c
compat.c
configs.c
cpu.c
cpuset.c [PATCH] cpuset: oom panic fix 2006-08-27 11:01:32 -07:00
delayacct.c [PATCH] task delay accounting fixes 2006-09-01 11:39:08 -07:00
dma.c
exec_domain.c
exit.c [PATCH] eligible_child: remove an obsolete ->tgid check 2006-09-02 14:51:27 -07:00
extable.c
fork.c [PATCH] task delay accounting fixes 2006-09-01 11:39:08 -07:00
futex.c [PATCH] Use the correct restart option for futex_lock_pi 2006-09-08 10:22:50 -07:00
futex_compat.c [PATCH] futex: Apply recent futex fixes to futex_compat 2006-08-06 08:57:49 -07:00
hrtimer.c [PATCH] fix hrtimer percpu usage typo 2006-08-14 12:54:28 -07:00
itimer.c
kallsyms.c
kexec.c
kfifo.c
kmod.c [PATCH] bug fix in kernel/kmod.c 2006-09-16 12:54:32 -07:00
kprobes.c
ksysfs.c
kthread.c
lockdep.c
lockdep_internals.h [PATCH] lockdep: double the number of stack-trace entries 2006-09-13 07:32:14 -07:00
lockdep_proc.c
module.c
mutex-debug.c
mutex-debug.h
mutex.c
mutex.h
panic.c [PATCH] lockdep: do not touch console state when tainting the kernel 2006-09-06 11:00:02 -07:00
params.c
pid.c
posix-cpu-timers.c
posix-timers.c
printk.c [PATCH] vt: printk: Fix framebuffer console triggering might_sleep assertion 2006-08-06 08:57:47 -07:00
profile.c
ptrace.c
rcupdate.c [PATCH] rcu_do_batch: make ->qlen decrement irq safe 2006-09-13 07:32:14 -07:00
rcutorture.c
relay.c
resource.c [PATCH] memory hotadd fixes: find_next_system_ram catch range fix 2006-08-06 08:57:48 -07:00
rtmutex-debug.c
rtmutex-debug.h
rtmutex-tester.c
rtmutex.c [PATCH] reference rt-mutex-design in rtmutex.c 2006-07-31 13:28:43 -07:00
rtmutex.h
rtmutex_common.h
rwsem.c
sched.c [PATCH] revert "Drop tasklist lock in do_sched_setscheduler" 2006-08-27 11:01:29 -07:00
seccomp.c
signal.c Fix force_sig_info() semantics after cleanups 2006-08-02 20:17:49 -07:00
softirq.c [PATCH] Reducing local_bh_enable/disable overhead in irqtrace 2006-07-31 13:28:42 -07:00
softlockup.c
spinlock.c [PATCH] lockdep ifdef fix 2006-09-06 11:00:01 -07:00
stacktrace.c
stop_machine.c [PATCH] Remove redundant up() in stop_machine() 2006-08-27 11:01:31 -07:00
sys.c
sys_ni.c
sysctl.c
taskstats.c
time.c
timer.c [PATCH] sys_getppid oopses on debug kernel 2006-08-14 12:54:29 -07:00
uid16.c
unwind.c
user.c
wait.c
workqueue.c [PATCH] workqueue: remove lock_cpu_hotplug() 2006-08-14 12:54:29 -07:00