Re: Fix quilt merge error in acpi-cpufreq.c

Ingo Molnar
2009-04-15T05:44:54Z

* Ingo Molnar <mingo@elte.hu> wrote:

> * Linux Kernel Mailing List <linux-kernel@vger.kernel.org> wrote:
>
> > Gitweb: http://git.kernel.org/linus/1c98aa7424ff163637d8321674ec58dee28152d4
> > Commit: 1c98aa7424ff163637d8321674ec58dee28152d4
> > Parent: 2e1c63b7ed36532b68f0eddd6a184d7ba1013b89
> > Author: Linus Torvalds <torvalds@linux-foundation.org>
> > AuthorDate: Mon Apr 13 18:09:20 2009 -0700
> > Committer: Linus Torvalds <torvalds@linux-foundation.org>
> > CommitDate: Mon Apr 13 18:09:20 2009 -0700
> >
> > Fix quilt merge error in acpi-cpufreq.c
> >
> > We ended up incorrectly using '&cur' instead of '&readin' in the
> > work_on_cpu() -> smp_call_function_single() transformation in commit
> > 01599fca6758d2cd133e78f87426fc851c9ea725 ("cpufreq: use
> > smp_call_function_[single|many]() in acpi-cpufreq.c").
> >
> > Andrew explains:
> > "OK, the acpi tree went and had conflicting changes merged into it after
> > I'd written the patch and it appears that I incorrectly reverted part
> > of 18b2646fe3babeb40b34a0c1751e0bf5adfdc64c while fixing the resulting
> > rejects.
> >
> > Switching it to `readin' looks correct."
> >
> > Acked-by: Andrew Morton <akpm@linux-foundation.org>
> > Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
> > ---
> > arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c | 2 +-
> > 1 files changed, 1 insertions(+), 1 deletions(-)
> >
> > diff --git a/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c b/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
> > index 3e3cd3d..837c2c4 100644
> > --- a/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
> > +++ b/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
> > @@ -277,7 +277,7 @@ static unsigned int get_measured_perf(struct cpufreq_policy *policy,
> > unsigned int perf_percent;
> > unsigned int retval;
> >
> > - if (smp_call_function_single(cpu, read_measured_perf_ctrs, &cur, 1))
> > + if (smp_call_function_single(cpu, read_measured_perf_ctrs, &readin, 1))
> > return 0;
>
> Ah, this might explain a few weird smp_processor_id() runtime
> warnings i got a few hours ago in that area of code (but didnt
> track it down at that time) when i updated to at around ~80a04d3.
>
> (Never noticed the build warning - there's still too many of
> them.)

No, that warning is back and triggered in overnight testing:

[ 54.888193] BUG: using smp_processor_id() in preemptible [00000000] code: S99local/7753
[ 54.888267] caller is smp_call_function_many+0x29/0x210
[ 54.888309] Pid: 7753, comm: S99local Not tainted 2.6.30-rc1-tip #1750
[ 54.888352] Call Trace:
[ 54.888389] [<c054d06d>] debug_smp_processor_id+0xcd/0xd0
[ 54.888432] [<c016e989>] smp_call_function_many+0x29/0x210
[ 54.888477] [<c0115860>] ? do_drv_write+0x0/0x70
[ 54.888519] [<c0115851>] drv_write+0x21/0x30
[ 54.888559] [<c0115e06>] acpi_cpufreq_target+0x146/0x310

fuller log below. I think this is because smp_call_function_many()
was essentially unused before - an IPI function should not trigger
this warning, it will naturally be called in preemptible context.

Rusty?

Ingo

----------------->
[ 40.227336] Adding 4096564k swap on /dev/sda2. Priority:-1 extents:1 across:4096564k
[ 43.958724] eth0: no IPv6 routers present
[ 54.827389] CPUFREQ: ondemand sampling_rate_max sysfs file is deprecated - used by: cat
[ 54.888193] BUG: using smp_processor_id() in preemptible [00000000] code: S99local/7753
[ 54.888267] caller is smp_call_function_many+0x29/0x210
[ 54.888309] Pid: 7753, comm: S99local Not tainted 2.6.30-rc1-tip #1750
[ 54.888352] Call Trace:
[ 54.888389] [<c054d06d>] debug_smp_processor_id+0xcd/0xd0
[ 54.888432] [<c016e989>] smp_call_function_many+0x29/0x210
[ 54.888477] [<c0115860>] ? do_drv_write+0x0/0x70
[ 54.888519] [<c0115851>] drv_write+0x21/0x30
[ 54.888559] [<c0115e06>] acpi_cpufreq_target+0x146/0x310
[ 54.888603] [<c0166aab>] ? trace_hardirqs_on_caller+0x1b/0x1b0
[ 54.888647] [<c0166c4b>] ? trace_hardirqs_on+0xb/0x10
[ 54.888690] [<c022fd78>] ? sysfs_remove_group+0x68/0xd0
[ 54.888735] [<c0f17e02>] ? __mutex_unlock_slowpath+0x172/0x180
[ 54.888781] [<c0115cc0>] ? acpi_cpufreq_target+0x0/0x310
[ 54.888828] [<c0c8141e>] __cpufreq_driver_target+0x5e/0xa0
[ 54.888873] [<c0c827a3>] cpufreq_governor_performance+0x23/0x30
[ 54.888918] [<c0c804cb>] __cpufreq_governor+0x2b/0x60
[ 54.888961] [<c015af6f>] ? blocking_notifier_call_chain+0x1f/0x30
[ 54.889006] [<c0c8076a>] __cpufreq_set_policy+0xfa/0x140
[ 54.889048] [<c0c80f9a>] store_scaling_governor+0x8a/0xb0
[ 54.889091] [<c0c81880>] ? handle_update+0x0/0x20
[ 54.889133] [<c0c80ea4>] ? cpufreq_cpu_get+0x74/0x90
[ 54.889174] [<c0c80f10>] ? store_scaling_governor+0x0/0xb0
[ 54.889217] [<c0c8195d>] store+0x4d/0x70
[ 54.889257] [<c022cc50>] flush_write_buffer+0x50/0x70
[ 54.889298] [<c022cd4c>] sysfs_write_file+0x4c/0x80
[ 54.889340] [<c01df6df>] vfs_write+0x8f/0xd0
[ 54.889379] [<c022cd00>] ? sysfs_write_file+0x0/0x80
[ 54.889421] [<c01df762>] sys_write+0x42/0x70
[ 54.889461] [<c0102fab>] sysenter_do_call+0x12/0x36
[ 54.889823] BUG: using smp_processor_id() in preemptible [00000000] code: S99local/7753
[ 54.889890] caller is smp_call_function_many+0x29/0x210
[ 54.889931] Pid: 7753, comm: S99local Not tainted 2.6.30-rc1-tip #1750
[ 54.889974] Call Trace:
[ 54.890008] [<c054d06d>] debug_smp_processor_id+0xcd/0xd0
[ 54.890051] [<c016e989>] smp_call_function_many+0x29/0x210
[ 54.890093] [<c0115860>] ? do_drv_write+0x0/0x70
[ 54.890133] [<c0115851>] drv_write+0x21/0x30
[ 54.890172] [<c0115e06>] acpi_cpufreq_target+0x146/0x310
[ 54.890216] [<c0166aab>] ? trace_hardirqs_on_caller+0x1b/0x1b0
[ 54.890261] [<c0166c4b>] ? trace_hardirqs_on+0xb/0x10
[ 54.890304] [<c022fd78>] ? sysfs_remove_group+0x68/0xd0
[ 54.890349] [<c0f17e02>] ? __mutex_unlock_slowpath+0x172/0x180
[ 54.890393] [<c0115cc0>] ? acpi_cpufreq_target+0x0/0x310
[ 54.890437] [<c0c8141e>] __cpufreq_driver_target+0x5e/0xa0
[ 54.890480] [<c0c827a3>] cpufreq_governor_performance+0x23/0x30
[ 54.890526] [<c0c804cb>] __cpufreq_governor+0x2b/0x60
[ 54.890569] [<c015af6f>] ? blocking_notifier_call_chain+0x1f/0x30
[ 54.890614] [<c0c8076a>] __cpufreq_set_policy+0xfa/0x140
[ 54.890658] [<c0c80f9a>] store_scaling_governor+0x8a/0xb0
[ 54.890701] [<c0c81880>] ? handle_update+0x0/0x20
[ 54.890743] [<c0c80ea4>] ? cpufreq_cpu_get+0x74/0x90
[ 54.890783] [<c0c80f10>] ? store_scaling_governor+0x0/0xb0
[ 54.890826] [<c0c8195d>] store+0x4d/0x70
[ 54.890864] [<c022cc50>] flush_write_buffer+0x50/0x70
[ 54.890994] [<c022cd4c>] sysfs_write_file+0x4c/0x80
[ 54.891035] [<c01df6df>] vfs_write+0x8f/0xd0
[ 54.891075] [<c022cd00>] ? sysfs_write_file+0x0/0x80
[ 54.891115] [<c01df762>] sys_write+0x42/0x70
[ 54.891154] [<c0102fab>] sysenter_do_call+0x12/0x36
[ 56.475977] device: 'vcs4': device_add