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Message-ID: <1293225065.16694.796.camel@pasglop> Date: Sat, 25 Dec 2010 08:11:05 +1100 From: Benjamin Herrenschmidt <benh@...nel.crashing.org> To: Steven Rostedt <rostedt@...dmis.org> Cc: LKML <linux-kernel@...r.kernel.org>, Andrew Morton <akpm@...ux-foundation.org>, Joerg Sommer <joerg@...a.gnuu.de>, linuxppc-dev <linuxppc-dev@...abs.org> Subject: Re: [PATCH][GIT PULL] powerpc64/tracing: Add frame buffer to calls of trace_hardirqs_on/off On Fri, 2010-12-24 at 00:46 -0500, Steven Rostedt wrote: > arch/powerpc/include/asm/irqflags.h | 40 ++++++++++++++++++++++++++-------- > 1 files changed, 30 insertions(+), 10 deletions(-) > --------------------------- > commit 5025019505da6731f8be13940bb978617599c935 > Author: Steven Rostedt <srostedt@...hat.com> > Date: Thu Dec 23 21:07:39 2010 -0800 > > powerpc64/tracing: Add frame buffer to calls of trace_hardirqs_on/off > > When an interrupt occurs in userspace, we can call trace_hardirqs_on/off() > With one level stack. But if we have irqsoff tracing enabled, > it checks both CALLER_ADDR0 and CALLER_ADDR1. The second call > goes two stack frames up. If this is from user space, then there may > not exist a second stack. > > Add a second stack when calling trace_hardirqs_on/off() otherwise > the following oops might occur: Hrm... this is really gross :-) So we add gratuituous overhead because the code below is dumb :-) What about making the code less stupid instead when poking at the stack and detect it's coming from userspace instead ? Cheers, Ben. > Oops: Kernel access of bad area, sig: 11 [#1] > PREEMPT SMP NR_CPUS=2 PA Semi PWRficient > last sysfs file: /sys/block/sda/size > Modules linked in: ohci_hcd ehci_hcd usbcore > NIP: c0000000000e1c00 LR: c0000000000034d4 CTR: 000000011012c440 > REGS: c00000003e2f3af0 TRAP: 0300 Not tainted (2.6.37-rc6+) > MSR: 9000000000001032 <ME,IR,DR> CR: 48044444 XER: 20000000 > DAR: 00000001ffb9db50, DSISR: 0000000040000000 > TASK = c00000003e1a00a0[2088] 'emacs' THREAD: c00000003e2f0000 CPU: 1 > GPR00: 0000000000000001 c00000003e2f3d70 c00000000084e0d0 c0000000008816e8 > GPR04: 000000001034c678 000000001032e8f9 0000000010336540 0000000040020000 > GPR08: 0000000040020000 00000001ffb9db40 c00000003e2f3e30 0000000060000000 > GPR12: 100000000000f032 c00000000fff0280 000000001032e8c9 0000000000000008 > GPR16: 00000000105be9c0 00000000105be950 00000000105be9b0 00000000105be950 > GPR20: 00000000ffb9dc50 00000000ffb9dbf0 00000000102f0000 00000000102f0000 > GPR24: 00000000102e0000 00000000102f0000 0000000010336540 c0000000009ded38 > GPR28: 00000000102e0000 c0000000000034d4 c0000000007ccb10 c00000003e2f3d70 > NIP [c0000000000e1c00] .trace_hardirqs_off+0xb0/0x1d0 > LR [c0000000000034d4] decrementer_common+0xd4/0x100 > Call Trace: > [c00000003e2f3d70] [c00000003e2f3e30] 0xc00000003e2f3e30 (unreliable) > [c00000003e2f3e30] [c0000000000034d4] decrementer_common+0xd4/0x100 > Instruction dump: > 81690000 7f8b0000 419e0018 f84a0028 60000000 60000000 60000000 e95f0000 > 80030000 e92a0000 eb6301f8 2f800000 <eb890010> 41fe00dc a06d000a eb1e8050 > ---[ end trace 4ec7fd2be9240928 ]--- > > Reported-by: Joerg Sommer <joerg@...a.gnuu.de> > Signed-off-by: Steven Rostedt <rostedt@...dmis.org> > > diff --git a/arch/powerpc/include/asm/irqflags.h b/arch/powerpc/include/asm/irqflags.h > index b85d8dd..b0b06d8 100644 > --- a/arch/powerpc/include/asm/irqflags.h > +++ b/arch/powerpc/include/asm/irqflags.h > @@ -12,24 +12,44 @@ > > #else > #ifdef CONFIG_TRACE_IRQFLAGS > +#ifdef CONFIG_IRQSOFF_TRACER > +/* > + * Since the ftrace irqsoff latency trace checks CALLER_ADDR1, > + * which is the stack frame here, we need to force a stack frame > + * in case we came from user space. > + */ > +#define TRACE_WITH_FRAME_BUFFER(func) \ > + mflr r0; \ > + stdu r1, -32(r1); \ > + std r0, 16(r1); \ > + stdu r1, -32(r1); \ > + bl func; \ > + ld r1, 0(r1); \ > + ld r1, 0(r1); > +#else > +#define TRACE_WITH_FRAME_BUFFER(func) \ > + bl func; > +#endif > + > /* > * Most of the CPU's IRQ-state tracing is done from assembly code; we > * have to call a C function so call a wrapper that saves all the > * C-clobbered registers. > */ > -#define TRACE_ENABLE_INTS bl .trace_hardirqs_on > -#define TRACE_DISABLE_INTS bl .trace_hardirqs_off > -#define TRACE_AND_RESTORE_IRQ_PARTIAL(en,skip) \ > - cmpdi en,0; \ > - bne 95f; \ > - stb en,PACASOFTIRQEN(r13); \ > - bl .trace_hardirqs_off; \ > - b skip; \ > -95: bl .trace_hardirqs_on; \ > +#define TRACE_ENABLE_INTS TRACE_WITH_FRAME_BUFFER(.trace_hardirqs_on) > +#define TRACE_DISABLE_INTS TRACE_WITH_FRAME_BUFFER(.trace_hardirqs_off) > + > +#define TRACE_AND_RESTORE_IRQ_PARTIAL(en,skip) \ > + cmpdi en,0; \ > + bne 95f; \ > + stb en,PACASOFTIRQEN(r13); \ > + TRACE_WITH_FRAME_BUFFER(.trace_hardirqs_off) \ > + b skip; \ > +95: TRACE_WITH_FRAME_BUFFER(.trace_hardirqs_on) \ > li en,1; > #define TRACE_AND_RESTORE_IRQ(en) \ > TRACE_AND_RESTORE_IRQ_PARTIAL(en,96f); \ > - stb en,PACASOFTIRQEN(r13); \ > + stb en,PACASOFTIRQEN(r13); \ > 96: > #else > #define TRACE_ENABLE_INTS > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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