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Consider a kernel crash in a module, simulated the following way:
static int my_init(void)
{
char *map = (void *)0x5;
*map = 3;
return 0;
}
module_init(my_init);
When we turn off FRAME_POINTERs, the very first instruction in
that function causes a BUG. The problem is that we print IP in
the BUG report using %pB (from printk_address). And %pB
decrements the pointer by one to fix printing addresses of
functions with tail calls.
This was added in commit 71f9e59800e5ad4 ("x86, dumpstack: Use
%pB format specifier for stack trace") to fix the call stack
printouts.
So instead of correct output:
BUG: unable to handle kernel NULL pointer dereference at 0000000000000005
IP: [<ffffffffa01ac000>] my_init+0x0/0x10 [pb173]
We get:
BUG: unable to handle kernel NULL pointer dereference at 0000000000000005
IP: [<ffffffffa0152000>] 0xffffffffa0151fff
To fix that, we use %pS only for stack addresses printouts (via
newly added printk_stack_address) and %pB for regs->ip (via
printk_address). I.e. we revert to the old behaviour for all
except call stacks. And since from all those reliable is 1, we
remove that parameter from printk_address.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: joe@perches.com
Cc: jirislaby@gmail.com
Link: http://lkml.kernel.org/r/1382706418-8435-1-git-send-email-jslaby@suse.cz
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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This reverts commit 8eba18428ac926f436064ac281e76d36d51bd631.
uv_trace() is not used by anything, nor is uv_trace_nmi_func, nor
uv_trace_func.
That's not how we do instrumentation code in the kernel: we add
tracepoints, printk()s, etc. so that everyone not just those with
magic kernel modules can debug a system.
So remove this unused (and misguied) piece of code.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Mike Travis <travis@sgi.com>
Cc: Dimitri Sivanich <sivanich@sgi.com>
Cc: Hedi Berriche <hedi@sgi.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Jason Wessel <jason.wessel@windriver.com>
Link: http://lkml.kernel.org/n/tip-tumfBffmr4jmnt8Gyxanoblg@git.kernel.org
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This patch restores the capability to enter KDB (and KGDB) from
the UV NMI handler. This is needed because the UV system
console is not capable of sending the 'break' signal to the
serial console port. It is also useful when the kernel is hung
in such a way that it isn't responding to normal external I/O,
so sending 'g' to sysreq-trigger does not work either.
Another benefit of the external NMI command is that all the cpus
receive the NMI signal at roughly the same time so they are more
closely aligned timewise.
It utilizes the newly added kgdb_nmicallin function to gain
entry to KGDB/KDB by the master. The slaves still enter via the
standard kgdb_nmicallback function. It also uses the new
'send_ready' pointer to tell KGDB/KDB to signal the slaves when
to proceed into the KGDB slave loop.
It is enabled when the nmi action is set to "kdb" and the kernel
is built with CONFIG_KDB enabled. Note that if kgdb is
connected that interface will be used instead.
Signed-off-by: Mike Travis <travis@sgi.com>
Reviewed-by: Dimitri Sivanich <sivanich@sgi.com>
Reviewed-by: Hedi Berriche <hedi@sgi.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Jason Wessel <jason.wessel@windriver.com>
Link: http://lkml.kernel.org/r/20131002151418.089692683@asylum.americas.sgi.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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GCC warned about:
arch/x86/platform/uv/uv_nmi.c: In function ‘uv_nmi_setup’:
arch/x86/platform/uv/uv_nmi.c:664:2: warning: the address of ‘uv_nmi_cpu_mask’ will always evaluate as ‘true’
The reason is this code:
alloc_cpumask_var(&uv_nmi_cpu_mask, GFP_KERNEL);
BUG_ON(!uv_nmi_cpu_mask);
which is not the way to check for alloc_cpumask_var() failures - its
return code should be checked instead.
Cc: Mike Travis <travis@sgi.com>
Link: http://lkml.kernel.org/n/tip-2pXRemsjupmvonbpmmnzleo1@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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This patch adds support for the uvtrace module by providing a
skeleton call to the registered trace function. It also
provides another separate 'NMI' tracer that is triggered by the
system wide 'power nmi' command.
Signed-off-by: Mike Travis <travis@sgi.com>
Reviewed-by: Dimitri Sivanich <sivanich@sgi.com>
Reviewed-by: Hedi Berriche <hedi@sgi.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Jason Wessel <jason.wessel@windriver.com>
Link: http://lkml.kernel.org/r/20130923212501.185052551@asylum.americas.sgi.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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If a system has hung and it no longer responds to external
events, this patch adds the capability of doing a standard kdump
and system reboot then triggered by the system NMI command.
It is enabled when the nmi action is changed to "kdump" and the
kernel is built with CONFIG_KEXEC enabled.
Signed-off-by: Mike Travis <travis@sgi.com>
Reviewed-by: Dimitri Sivanich <sivanich@sgi.com>
Reviewed-by: Hedi Berriche <hedi@sgi.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Jason Wessel <jason.wessel@windriver.com>
Link: http://lkml.kernel.org/r/20130923212500.660567460@asylum.americas.sgi.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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The standard NMI handler dumps the states of all the cpus. This
includes a full register dump and stack trace. This can be way
more information than what is needed. This patch adds a
"summary" dump that is basically a form of the "ps" command. It
includes the symbolic IP address as well as the command field
and basic process information.
It is enabled when the nmi action is changed to "ips".
Signed-off-by: Mike Travis <travis@sgi.com>
Reviewed-by: Dimitri Sivanich <sivanich@sgi.com>
Reviewed-by: Hedi Berriche <hedi@sgi.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Jason Wessel <jason.wessel@windriver.com>
Link: http://lkml.kernel.org/r/20130923212500.507922930@asylum.americas.sgi.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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The current UV NMI handler has not been updated for the changes
in the system NMI handler and the perf operations. The UV NMI
handler reads an MMR in the UV Hub to check to see if the NMI
event was caused by the external 'system NMI' that the operator
can initiate on the System Mgmt Controller.
The problem arises when the perf tools are running, causing
millions of perf events per second on very large CPU count
systems. Previously this was okay because the perf NMI handler
ran at a higher priority on the NMI call chain and if the NMI
was a perf event, it would stop calling other NMI handlers
remaining on the NMI call chain.
Now the system NMI handler calls all the handlers on the NMI
call chain including the UV NMI handler. This causes the UV NMI
handler to read the MMRs at the same millions per second rate.
This can lead to significant performance loss and possible
system failures. It also can cause thousands of 'Dazed and
Confused' messages being sent to the system console. This
effectively makes perf tools unusable on UV systems.
To avoid this excessive overhead when perf tools are running,
this code has been optimized to minimize reading of the MMRs as
much as possible, by moving to the NMI_UNKNOWN notifier chain.
This chain is called only when all the users on the standard
NMI_LOCAL call chain have been called and none of them have
claimed this NMI.
There is an exception where the NMI_LOCAL notifier chain is
used. When the perf tools are in use, it's possible that the UV
NMI was captured by some other NMI handler and then either
ignored or mistakenly processed as a perf event. We set a
per_cpu ('ping') flag for those CPUs that ignored the initial
NMI, and then send them an IPI NMI signal. The NMI_LOCAL
handler on each cpu does not need to read the MMR, but instead
checks the in memory flag indicating it was pinged. There are
two module variables, 'ping_count' indicating how many requested
NMI events occurred, and 'ping_misses' indicating how many stray
NMI events. These most likely are perf events so it shows the
overhead of the perf NMI interrupts and how many MMR reads were avoided.
This patch also minimizes the reads of the MMRs by having the
first cpu entering the NMI handler on each node set a per HUB
in-memory atomic value. (Having a per HUB value avoids sending
lock traffic over NumaLink.) Both types of UV NMIs from the SMI
layer are supported.
Signed-off-by: Mike Travis <travis@sgi.com>
Reviewed-by: Dimitri Sivanich <sivanich@sgi.com>
Reviewed-by: Hedi Berriche <hedi@sgi.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Jason Wessel <jason.wessel@windriver.com>
Link: http://lkml.kernel.org/r/20130923212500.353547733@asylum.americas.sgi.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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This patch moves the UV NMI support from the x2apic file to a
new separate uv_nmi.c file in preparation for the next sequence
of patches. It prevents upcoming bloat of the x2apic file, and
has the added benefit of putting the upcoming /sys/module
parameters under the name 'uv_nmi' instead of 'x2apic_uv_x',
which was obscure.
Signed-off-by: Mike Travis <travis@sgi.com>
Reviewed-by: Dimitri Sivanich <sivanich@sgi.com>
Reviewed-by: Hedi Berriche <hedi@sgi.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Jason Wessel <jason.wessel@windriver.com>
Link: http://lkml.kernel.org/r/20130923212500.183295611@asylum.americas.sgi.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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