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SubjectRe: [Patch -tip 0/4] Creation of the initcall tracer

* Frédéric Weisbecker <fweisbec@gmail.com> wrote:

> Ingo Molnar a écrit :
> > * Ingo Molnar <mingo@elte.hu> wrote:
> >
> >> i've integrated tip/tracing/fastboot into tip/master and have started
> >> testing it. It passed the basic tests already so i've just pushed out
> >> the new tip/master. Please double-check that i have not messed up the
> >> rename or the integration somewhere.
> >
> > FYI, -tip testing found a boot hang with CONFIG_BOOT_TRACER=y, on a
> > 32-bit T60 laptop. I've attached the config that provokes the hang. (you
> > need initcall_debug on the boot commandline)
> >
> > The hang always happens after a specific initcall, shortly after tracing
> > is enabled. It just hangs indefinitely there, the last line displayed
> > was:
> >
> > [ 0.004017] initcall ehci_hcd_init+0x0/0x80 returned 0 after 228 msecs
> >
> > it should have printed this next:
> >
> > [ 0.808024] calling ohci_hcd_mod_init+0x0/0x80 @ 10
> >
> > but that line is never printed.
> >
> > i've bisected the hang down to this specific commit:
> >
> > | 35df98dfe2b2503436a8cfda301657810df50a3a is first bad commit
> > | commit 35df98dfe2b2503436a8cfda301657810df50a3a
> > | Author: Frédéric Weisbecker <fweisbec@gmail.com>
> > | Date: Tue Sep 23 11:38:18 2008 +0100
> > |
> > | tracing/ftrace: launch boot tracing after pre-smp initcalls
> >
> > An idea: maybe the boot tracer is interacting with the ftrace self-tests
> > somehow? CONFIG_FTRACE_SELFTEST=y is enabled.
> >
> > another thing i noticed is that the sysprof tracer was initialized and
> > self-tested shortly before the hang occured. Might be unrelated.
> >
> > the bisection log is:
> >
> > # bad: [6522eab5] Merge branch 'x86/uv'
> > # good: [699b81f5] Merge branch 'x86/iommu'
> > # bad: [8007aae9] timers: fix build error in !oneshot case
> > # good: [7f29b23d] Merge branch 'core/rcu'
> > # bad: [a54f17e3] manual merge of tracing/fastboot
> > # good: [bcbbe946] tracing/ftrace: make tracing suitable to run the b
> > # good: [d7095e5a] Merge branch 'fastboot'
> > # bad: [35df98df] tracing/ftrace: launch boot tracing after pre-smp
> > # good: [42aaa6be] tracing/ftrace: give an entry on the config for bo
> >
> > Ingo
> >
> Ingo Molnar a écrit :
> > * Ingo Molnar <mingo@elte.hu> wrote:
> >
> >> i've integrated tip/tracing/fastboot into tip/master and have started
> >> testing it. It passed the basic tests already so i've just pushed out
> >> the new tip/master. Please double-check that i have not messed up the
> >> rename or the integration somewhere.
> >
> > FYI, -tip testing found a boot hang with CONFIG_BOOT_TRACER=y, on a
> > 32-bit T60 laptop. I've attached the config that provokes the hang. (you
> > need initcall_debug on the boot commandline)
> >
> > The hang always happens after a specific initcall, shortly after tracing
> > is enabled. It just hangs indefinitely there, the last line displayed
> > was:
> >
> > [ 0.004017] initcall ehci_hcd_init+0x0/0x80 returned 0 after 228 msecs
> >
> > it should have printed this next:
> >
> > [ 0.808024] calling ohci_hcd_mod_init+0x0/0x80 @ 10
> >
> > but that line is never printed.
> >
> > i've bisected the hang down to this specific commit:
> >
> > | 35df98dfe2b2503436a8cfda301657810df50a3a is first bad commit
> > | commit 35df98dfe2b2503436a8cfda301657810df50a3a
> > | Author: Frédéric Weisbecker <fweisbec@gmail.com>
> > | Date: Tue Sep 23 11:38:18 2008 +0100
> > |
> > | tracing/ftrace: launch boot tracing after pre-smp initcalls
> >
> > An idea: maybe the boot tracer is interacting with the ftrace self-tests
> > somehow? CONFIG_FTRACE_SELFTEST=y is enabled.
> >
> > another thing i noticed is that the sysprof tracer was initialized and
> > self-tested shortly before the hang occured. Might be unrelated.
> >
> > the bisection log is:
> >
> > # bad: [6522eab5] Merge branch 'x86/uv'
> > # good: [699b81f5] Merge branch 'x86/iommu'
> > # bad: [8007aae9] timers: fix build error in !oneshot case
> > # good: [7f29b23d] Merge branch 'core/rcu'
> > # bad: [a54f17e3] manual merge of tracing/fastboot
> > # good: [bcbbe946] tracing/ftrace: make tracing suitable to run the b
> > # good: [d7095e5a] Merge branch 'fastboot'
> > # bad: [35df98df] tracing/ftrace: launch boot tracing after pre-smp
> > # good: [42aaa6be] tracing/ftrace: give an entry on the config for bo
> >
> > Ingo
> >
>
> Hehe! I was preparing a patch because I saw last night that the self-tests were reseting and touching the ring-buffer during the initcall tracing.
> And now I can see the results of this problem....
>
> Following is a patch that should fix it.

applied to tip/tracing/fastboot, thanks Frédéric!

Ingo
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