For some time each panic() called with interrupts disabled
triggered the !irqs_disabled() WARN_ON in smp_call_function(),
producing ugly backtraces and confusing users.
This is a common situation with machine checks for example which
tend to call panic with interrupts disabled, but will also hit
in other situations e.g. panic during early boot. In fact it
means that panic cannot be called in many circumstances, which
would be bad.
This all started with the new fancy queued smp_call_function,
which is then used by the shutdown path to shut down the other
CPUs.
On closer examination it turned out that the fancy RCU
smp_call_function() does lots of things not suitable in a panic
situation anyways, like allocating memory and relying on complex
system state.
I originally tried to patch this over by checking for panic
there, but it was quite complicated and the original patch
was also not very popular. This also didn't fix some of the
underlying complexity problems.
The new code in post 2.6.29 tries to patch around this by
checking for oops_in_progress, but that is not enough to make
this fully safe and I don't think that's a real solution
because panic has to be reliable.
So instead use an own vector to reboot. This makes the reboot
code extremly straight forward, which is definitely a big plus
in a panic situation where it is important to avoid relying on
too much kernel state. The new simple code is also safe to be
called from interupts off region because it is very very simple.
There can be situations where it is important that panic
is reliable. For example on a fatal machine check the panic
is needed to get the system up again and running as quickly
as possible. So it's important that panic is reliable and
all function it calls simple.
This is why I came up with this simple vector scheme.
It's very hard to beat in simplicity. Vectors are not
particularly precious anymore since all big systems are
using per CPU vectors.
Another possibility would have been to use an NMI similar
to kdump, but there is still the problem that NMIs don't
work reliably on some systems due to BIOS issues. NMIs
would have been able to stop CPUs running with interrupts
off too. In the sake of universal reliability I opted for
using a non NMI vector for now.
I put the reboot vector into the highest priority bucket of
the APIC vectors and moved the 64bit UV_BAU message down
instead into the next lower priority.
[ Impact: bug fix, fixes an old regression ]
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Machine checks support waking up the mcelog daemon quickly.
The original wake up code for this was pretty ugly, relying on
a idle notifier and a special process flag. The reason it did
it this way is that the machine check handler is not subject
to normal interrupt locking rules so it's not safe
to call wake_up(). Instead it set a process flag
and then either did the wakeup in the syscall return
or in the idle notifier.
This patch adds a new "bootstraping" method as replacement.
The idea is that the handler checks if it's in a state where
it is unsafe to call wake_up(). If it's safe it calls it directly.
When it's not safe -- that is it interrupted in a critical
section with interrupts disables -- it uses a new "self IPI" to trigger
an IPI to its own CPU. This can be done safely because IPI
triggers are atomic with some care. The IPI is raised
once the interrupts are reenabled and can then safely call
wake_up().
When APICs are disabled the event is just queued and will be picked up
eventually by the next polling timer. I think that's a reasonable
compromise, since it should only happen quite rarely.
Contains fixes from Ying Huang.
[ solve conflict on irqinit, make it work on 32bit (entry_arch.h) - HS ]
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Merge reason: arch/x86/kernel/irqinit_{32,64}.c unified in irq/numa
and modified in x86/mce3; this merge resolves the conflict.
Conflicts:
arch/x86/kernel/irqinit.c
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Impact: fix crash with many devices
I found this crash:
[ 552.616646] general protection fault: 0403 [#1] SMP
[ 552.620013] last sysfs file:
/sys/devices/pci0000:00/0000:00:02.0/usb1/1-1/1-1:1.0/host13/target13:0:0/13:0:0:0/block/sr0/size
[ 552.620013] CPU 0
[ 552.620013] Modules linked in:
[ 552.620013] Pid: 0, comm: swapper Not tainted 2.6.30-rc1-tip-01931-g8fcafd8-dirty #28 Sun Fire X4440
[ 552.620013] RIP: 0010:[<ffffffff8023bada>] [<ffffffff8023bada>] default_idle+0x7d/0xda
[ 552.620013] RSP: 0018:ffffffff81345e68 EFLAGS: 00010246
[ 552.620013] RAX: 0000000000000000 RBX: ffffffff8133d870 RCX: ffffc20000000000
[ 552.620013] RDX: 00000000001d0620 RSI: ffffffff8023bad8 RDI: ffffffff802a3169
[ 552.620013] RBP: ffffffff81345e98 R08: 0000000000000000 R09: ffffffff812244a0
[ 552.620013] R10: ffffffff81345dc8 R11: 7ebe1b6fa0bcac50 R12: 4ec4ec4ec4ec4ec5
[ 552.620013] R13: ffffffff813a54d0 R14: ffffffff813a7a40 R15: 0000000000000000
[ 552.620013] FS: 00000000006d1880(0000) GS:ffffc20000000000(0000) knlGS:0000000000000000
[ 552.620013] CS: 0010 DS: 0018 ES: 0018 CR0: 000000008005003b
[ 552.620013] CR2: 00007fec9d936a50 CR3: 000000007d1a9000 CR4: 00000000000006e0
[ 552.620013] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 552.620013] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[ 552.620013] Process swapper (pid: 0, threadinfo ffffffff81344000,task ffffffff812244a0)
[ 552.620013] Stack:
[ 552.620013] 0000000000000000 ffffc20000000000 00000000001d0620 7ebe1b6fa0bcac50
[ 552.620013] ffffffff8133d870 4ec4ec4ec4ec4ec5 ffffffff81345ec8 ffffffff8023bd84
[ 552.620013] 4ec4ec4ec4ec4ec5 ffffffff813a54d0 7ebe1b6fa0bcac50 ffffffff8133d870
[ 552.620013] Call Trace:
[ 552.620013] [<ffffffff8023bd84>] c1e_idle+0x109/0x124
[ 552.620013] [<ffffffff8023314b>] cpu_idle+0xb8/0x101
[ 552.620013] [<ffffffff80c16d6a>] rest_init+0x7e/0x94
[ 552.620013] [<ffffffff81357efc>] start_kernel+0x3dc/0x3fd
[ 552.620013] [<ffffffff813572a9>] x86_64_start_reservations+0xb9/0xd4
[ 552.620013] [<ffffffff813573b2>] x86_64_start_kernel+0xee/0x109
[ 552.620013] Code: 48 8b 04 25 f8 b4 00 00 83 a0 3c e0 ff ff fb 0f ae f0 65 48 8b 04 25 f8 b4 00 00 f6 80 38 e0 ff ff 08 75 09 e8 71 76 06 00 fb f4 <eb> 06 e8 68 76 06 00 fb 65 48 8b 04 25 f8 b4 00 00 83 88 3c e0
[ 552.620013] RIP [<ffffffff8023bada>] default_idle+0x7d/0xda
[ 552.620013] RSP <ffffffff81345e68>
[ 552.828646] ---[ end trace 4cbfc5c01382af7f ]---
Joerg Roedel said
"The 0403 error code means that there was an external interrupt with vector
0x80. Yinghai, my theory is that the kernel on this machine has no 32bit
emulation compiled in, right? In this case the selector points to a zero entry
which may cause the #gpf right after the hlt.
But I have no idea where the external int 0x80 comes from"
it turns out that we could use 0x80 for external device on 64-bit
when 32-bit emulation is disabled.
But we forgot to set the gate for it.
try to set gate for it by checking used_vectors.
Also move apic_intr_init() early to avoid setting
that gate two times.
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Joerg Roedel <joerg.roedel@amd.com>
LKML-Reference: <49E62DFD.6010904@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
To make the topic merge life easier for tip:perfcounters/core,
include two (inactive in this topic) IRQ vector initializations
here.
Also fix build bug - missing kprobes.h inclusion.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: cleanup
We can remove some #ifdefs if we define IA32_SYSCALL_VECTOR on 32-bit.
Reviewed-by Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Ingo Molnar