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kernel 3.19.1 kernel/built-in.o #100

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satyapendem opened this issue Aug 28, 2016 · 2 comments
Closed

kernel 3.19.1 kernel/built-in.o #100

satyapendem opened this issue Aug 28, 2016 · 2 comments

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@satyapendem
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*_kernel/built-in.o : In function 'do_adjtimex' (.text+0x5020e): undefined reference to '_do_adjtimex any plz help with that i'm trying to make linux 3.19 to 3.19.1
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@RobertCNelson
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Active support is on the 4.4 branch

Regards,

@satyapendem
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thank you.

RobertCNelson pushed a commit that referenced this issue Dec 17, 2021
@nathanlynch @gregkh
powerpc/smp: do not decrement idle task preempt count in CPU offline
53770a4 
[ Upstream commit 787252a ]

With PREEMPT_COUNT=y, when a CPU is offlined and then onlined again, we
get:

BUG: scheduling while atomic: swapper/1/0/0x00000000
no locks held by swapper/1/0.
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.15.0-rc2+ #100
Call Trace:
 dump_stack_lvl+0xac/0x108
 __schedule_bug+0xac/0xe0
 __schedule+0xcf8/0x10d0
 schedule_idle+0x3c/0x70
 do_idle+0x2d8/0x4a0
 cpu_startup_entry+0x38/0x40
 start_secondary+0x2ec/0x3a0
 start_secondary_prolog+0x10/0x14

This is because powerpc's arch_cpu_idle_dead() decrements the idle task's
preempt count, for reasons explained in commit a7c2bb8 ("powerpc:
Re-enable preemption before cpu_die()"), specifically "start_secondary()
expects a preempt_count() of 0."

However, since commit 2c669ef ("powerpc/preempt: Don't touch the idle
task's preempt_count during hotplug") and commit f1a0a37 ("sched/core:
Initialize the idle task with preemption disabled"), that justification no
longer holds.

The idle task isn't supposed to re-enable preemption, so remove the
vestigial preempt_enable() from the CPU offline path.

Tested with pseries and powernv in qemu, and pseries on PowerVM.

Fixes: 2c669ef ("powerpc/preempt: Don't touch the idle task's preempt_count during hotplug")
Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Reviewed-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211015173902.2278118-1-nathanl@linux.ibm.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
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@RobertCNelson @satyapendem