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kernel 3.19.1 kernel/built-in.o #100
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Active support is on the 4.4 branch Regards, |
thank you. |
RobertCNelson
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Dec 17, 2021
[ 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 <[email protected]> Reviewed-by: Valentin Schneider <[email protected]> Reviewed-by: Srikar Dronamraju <[email protected]> Signed-off-by: Michael Ellerman <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Sasha Levin <[email protected]>
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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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