linux.git/drivers/char/sysrq.c, branch v2.6.32

perf: Do the big rename: Performance Counters -> Performance Events

2009-09-21T12:28:04+00:00

Bye-bye Performance Counters, welcome Performance Events!

In the past few months the perfcounters subsystem has grown out its
initial role of counting hardware events, and has become (and is
becoming) a much broader generic event enumeration, reporting, logging,
monitoring, analysis facility.

Naming its core object 'perf_counter' and naming the subsystem
'perfcounters' has become more and more of a misnomer. With pending
code like hw-breakpoints support the 'counter' name is less and
less appropriate.

All in one, we've decided to rename the subsystem to 'performance
events' and to propagate this rename through all fields, variables
and API names. (in an ABI compatible fashion)

The word 'event' is also a bit shorter than 'counter' - which makes
it slightly more convenient to write/handle as well.

Thanks goes to Stephane Eranian who first observed this misnomer and
suggested a rename.

User-space tooling and ABI compatibility is not affected - this patch
should be function-invariant. (Also, defconfigs were not touched to
keep the size down.)

This patch has been generated via the following script:

  FILES=$(find * -type f | grep -vE 'oprofile|[^K]config')

  sed -i \
    -e 's/PERF_EVENT_/PERF_RECORD_/g' \
    -e 's/PERF_COUNTER/PERF_EVENT/g' \
    -e 's/perf_counter/perf_event/g' \
    -e 's/nb_counters/nb_events/g' \
    -e 's/swcounter/swevent/g' \
    -e 's/tpcounter_event/tp_event/g' \
    $FILES

  for N in $(find . -name perf_counter.[ch]); do
    M=$(echo $N | sed 's/perf_counter/perf_event/g')
    mv $N $M
  done

  FILES=$(find . -name perf_event.*)

  sed -i \
    -e 's/COUNTER_MASK/REG_MASK/g' \
    -e 's/COUNTER/EVENT/g' \
    -e 's/\/event_id/g' \
    -e 's/counter/event/g' \
    -e 's/Counter/Event/g' \
    $FILES

... to keep it as correct as possible. This script can also be
used by anyone who has pending perfcounters patches - it converts
a Linux kernel tree over to the new naming. We tried to time this
change to the point in time where the amount of pending patches
is the smallest: the end of the merge window.

Namespace clashes were fixed up in a preparatory patch - and some
stylistic fallout will be fixed up in a subsequent patch.

( NOTE: 'counters' are still the proper terminology when we deal
  with hardware registers - and these sed scripts are a bit
  over-eager in renaming them. I've undone some of that, but
  in case there's something left where 'counter' would be
  better than 'event' we can undo that on an individual basis
  instead of touching an otherwise nicely automated patch. )

Suggested-by: Stephane Eranian 
Acked-by: Peter Zijlstra 
Acked-by: Paul Mackerras 
Reviewed-by: Arjan van de Ven 
Cc: Mike Galbraith 
Cc: Arnaldo Carvalho de Melo 
Cc: Frederic Weisbecker 
Cc: Steven Rostedt 
Cc: Benjamin Herrenschmidt 
Cc: David Howells 
Cc: Kyle McMartin 
Cc: Martin Schwidefsky 
Cc: "David S. Miller" 
Cc: Thomas Gleixner 
Cc: "H. Peter Anvin" 
Cc: 
LKML-Reference: 
Signed-off-by: Ingo Molnar

debug lockups: Improve lockup detection, fix generic arch fallback

2009-08-03T07:56:52+00:00

As Andrew noted, my previous patch ("debug lockups: Improve lockup
detection") broke/removed SysRq-L support from architecture that do
not provide a __trigger_all_cpu_backtrace implementation.

Restore a fallback path and clean up the SysRq-L machinery a bit:

 - Rename the arch method to arch_trigger_all_cpu_backtrace()

 - Simplify the define

 - Document the method a bit - in the hope of more architectures
   adding support for it.

[ The patch touches Sparc code for the rename. ]

Cc: Paul E. McKenney 
Cc: Peter Zijlstra 
Cc: Andrew Morton 
Cc: Linus Torvalds 
Cc: "David S. Miller" 
LKML-Reference: <20090802140809.7ec4bb6b.akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar

debug lockups: Improve lockup detection

2009-08-02T11:27:17+00:00

When debugging a recent lockup bug i found various deficiencies
in how our current lockup detection helpers work:

 - SysRq-L is not very efficient as it uses a workqueue, hence
   it cannot punch through hard lockups and cannot see through
   most soft lockups either.

 - The SysRq-L code depends on the NMI watchdog - which is off
   by default.

 - We dont print backtraces from the RCU code's built-in
   'RCU state machine is stuck' debug code. This debug
   code tends to be one of the first (and only) mechanisms
   that show that a lockup has occured.

This patch changes the code so taht we:

 - Trigger the NMI backtrace code from SysRq-L instead of using
   a workqueue (which cannot punch through hard lockups)

 - Trigger print-all-CPU-backtraces from the RCU lockup detection
   code

Also decouple the backtrace printing code from the NMI watchdog:

 - Dont use variable size cpumasks (it might not be initialized
   and they are a bit more fragile anyway)

 - Trigger an NMI immediately via an IPI, instead of waiting
   for the NMI tick to occur. This is a lot faster and can
   produce more relevant backtraces. It will also work if the
   NMI watchdog is disabled.

 - Dont print the 'dazed and confused' message when we print
   a backtrace from the NMI

 - Do a show_regs() plus a dump_stack() to get maximum info
   out of the dump. Worst-case we get two stacktraces - which
   is not a big deal. Sometimes, if register content is
   corrupted, the precise stack walker in show_regs() wont
   give us a full backtrace - in this case dump_stack() will
   do it.

Cc: Paul E. McKenney 
Cc: Peter Zijlstra 
Cc: Andrew Morton 
Cc: Linus Torvalds 
LKML-Reference: 
Signed-off-by: Ingo Molnar

sysrq, kdump: make sysrq-c consistent

2009-07-30T02:10:36+00:00

commit d6580a9f15238b87e618310c862231ae3f352d2d ("kexec: sysrq: simplify
sysrq-c handler") changed the behavior of sysrq-c to unconditional
dereference of NULL pointer.  So in cases with CONFIG_KEXEC, where
crash_kexec() was directly called from sysrq-c before, now it can be said
that a step of "real oops" was inserted before starting kdump.

However, in contrast to oops via SysRq-c from keyboard which results in
panic due to in_interrupt(), oops via "echo c > /proc/sysrq-trigger" will
not become panic unless panic_on_oops=1.  It means that even if dump is
properly configured to be taken on panic, the sysrq-c from proc interface
might not start crashdump while the sysrq-c from keyboard can start
crashdump.  This confuses traditional users of kdump, i.e.  people who
expect sysrq-c to do common behavior in both of the keyboard and proc
interface.

This patch brings the keyboard and proc interface behavior of sysrq-c in
line, by forcing panic_on_oops=1 before oops in sysrq-c handler.

And some updates in documentation are included, to clarify that there is
no longer dependency with CONFIG_KEXEC, and that now the system can just
crash by sysrq-c if no dump mechanism is configured.

Signed-off-by: Hidetoshi Seto 
Cc: Lai Jiangshan 
Cc: Ken'ichi Ohmichi 
Acked-by: Neil Horman 
Acked-by: Vivek Goyal 
Cc: Brayan Arraes 
Cc: Eric W. Biederman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kexec: sysrq: simplify sysrq-c handler

2009-06-18T20:03:59+00:00

Currently the sysrq-c handler is bit over-engineered.  Its behavior is
dependent on a few compile time and run time factors that alter its
behavior which is really unnecessecary.

If CONFIG_KEXEC is not configured, sysrq-c, crashes the system with a NULL
pointer dereference.  If CONFIG_KEXEC is configured, it calls crash_kexec
directly, which implies that the kexec kernel will either be booted (if
its been previously loaded), or it will simply do nothing (the no kexec
kernel has been loaded).

It would be much easier to just simplify the whole thing to dereference a
NULL pointer all the time regardless of configuration.  That way, it will
always try to crash the system, and if a kexec kernel has been loaded into
reserved space, it will still boot from the page fault trap handler
(assuming panic_on_oops is set appropriately).

[akpm@linux-foundation.org: build fix]
Signed-off-by: Neil Horman 
Acked-by: Vivek Goyal 
Cc: Brayan Arraes 
Cc: "Eric W. Biederman" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge commit 'v2.6.30-rc6' into perfcounters/core

2009-05-18T05:37:49+00:00

Merge reason: this branch was on an -rc4 base, merge it up to -rc6
              to get the latest upstream fixes.

Signed-off-by: Ingo Molnar

sysrq, intel_fb: fix sysrq g collision

2009-05-15T12:56:24+00:00

Commit 79e539453b34e35f39299a899d263b0a1f1670bd introduced a
regression where you cannot use sysrq 'g' to enter kgdb.  The solution
is to move the intel fb sysrq over to V for video instead of G for
graphics.  The SMP VOYAGER code to register for the sysrq-v is not
anywhere to be found in the mainline kernel, so the comments in the
code were cleaned up as well.

This patch also cleans up the sysrq definitions for kgdb to make it
generic for the kernel debugger, such that the sysrq 'g' can be used
in the future to enter a gdbstub or another kernel debugger.

Signed-off-by: Jason Wessel 
Acked-by: Jesse Barnes 
Acked-by: Randy Dunlap 
Signed-off-by: Andrew Morton

Merge branch 'linus' into perfcounters/core

2009-04-29T12:47:05+00:00

Merge reason: This brach was on -rc1, refresh it to almost-rc4 to pick up
              the latest upstream fixes.

Signed-off-by: Ingo Molnar

sysrq: remove duplicated #include

2009-04-13T22:04:31+00:00

Remove duplicated #include in drivers/char/sysrq.c.

Signed-off-by: Huang Weiyi 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge branch 'linus' into perfcounters/core-v2

2009-04-06T07:02:57+00:00

Merge reason: we have gathered quite a few conflicts, need to merge upstream

Conflicts:
	arch/powerpc/kernel/Makefile
	arch/x86/ia32/ia32entry.S
	arch/x86/include/asm/hardirq.h
	arch/x86/include/asm/unistd_32.h
	arch/x86/include/asm/unistd_64.h
	arch/x86/kernel/cpu/common.c
	arch/x86/kernel/irq.c
	arch/x86/kernel/syscall_table_32.S
	arch/x86/mm/iomap_32.c
	include/linux/sched.h
	kernel/Makefile

Signed-off-by: Ingo Molnar