Messages in this thread Patch in this message | | | Date | Wed, 28 Apr 2010 20:09:16 +0300 | From | Phil Carmody <> | Subject | Re: [GIT PULL] updates for oprofile |
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On 28/04/10 18:59 +0200, ext Robert Richter wrote: > On 27.04.10 20:47:51, Siarhei Siamashka wrote: > > Isn't hrtimer callback function supposed to be only called from IRQ context > > after this cleanup: http://lwn.net/Articles/308545/ ? > > Yes, the patch is upstream since v2.6.29. Thanks Siarhei. > > I will add a null pointer check anyway.
A few here thrashed around a couple of ideas, and the general consensus was that the following work for us, and is offered for consideration.
Phil
From: Phil Carmody <ext-phil.2.carmody@nokia.com> Date: Tue, 27 Apr 2010 19:28:33 +0300 Subject: [PATCH v2 1/1] oprofile: HACK - protect from not being in an IRQ context
http://lkml.org/lkml/2010/4/27/285
Protect against dereferencing regs when it's NULL, and force a magic number into pc to prevent too deep processing. This approach permits the dropped samples to be tallied as invalid Instruction Pointer events.
e.g. output from about 15mins at 10kHz sample rate: Nr. samples received: 2565380 Nr. samples lost invalid pc: 4
Signed-off-by: Phil Carmody <ext-phil.2.carmody@nokia.com> --- drivers/oprofile/cpu_buffer.c | 12 +++++++++--- 1 files changed, 9 insertions(+), 3 deletions(-)
diff --git a/drivers/oprofile/cpu_buffer.c b/drivers/oprofile/cpu_buffer.c index a7aae24..f70f954 100644 --- a/drivers/oprofile/cpu_buffer.c +++ b/drivers/oprofile/cpu_buffer.c @@ -357,9 +357,15 @@ void oprofile_add_ext_sample(unsigned long pc, struct pt_regs * const regs, void oprofile_add_sample(struct pt_regs * const regs, unsigned long event) { - int is_kernel = !user_mode(regs); - unsigned long pc = profile_pc(regs); - + int is_kernel; + unsigned long pc; + if (likely(regs)) { + is_kernel = !user_mode(regs); + pc = profile_pc(regs); + } else { + is_kernel = 0; /* This value will not be used */ + pc = ESCAPE_CODE; /* as this causes an early return. */ + } __oprofile_add_ext_sample(pc, regs, event, is_kernel); } -- 1.6.0.4
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