Revision 787252a10d9422f3058df9a4821f389e5326c440 authored by Nathan Lynch on 15 October 2021, 17:39:02 UTC, committed by Michael Ellerman on 20 October 2021, 10:38:01 UTC
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 a7c2bb8279d2 ("powerpc: Re-enable preemption before cpu_die()"), specifically "start_secondary() expects a preempt_count() of 0." However, since commit 2c669ef6979c ("powerpc/preempt: Don't touch the idle task's preempt_count during hotplug") and commit f1a0a376ca0c ("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: 2c669ef6979c ("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
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File | Mode | Size |
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platform | ||
acbuffer.h | -rw-r--r-- | 8.9 KB |
acconfig.h | -rw-r--r-- | 7.4 KB |
acexcep.h | -rw-r--r-- | 16.9 KB |
acnames.h | -rw-r--r-- | 2.2 KB |
acoutput.h | -rw-r--r-- | 16.4 KB |
acpi.h | -rw-r--r-- | 1.3 KB |
acpi_bus.h | -rw-r--r-- | 20.4 KB |
acpi_drivers.h | -rw-r--r-- | 2.6 KB |
acpi_io.h | -rw-r--r-- | 889 bytes |
acpi_lpat.h | -rw-r--r-- | 1.2 KB |
acpi_numa.h | -rw-r--r-- | 970 bytes |
acpiosxf.h | -rw-r--r-- | 11.3 KB |
acpixf.h | -rw-r--r-- | 30.6 KB |
acrestyp.h | -rw-r--r-- | 19.0 KB |
actbl.h | -rw-r--r-- | 18.3 KB |
actbl1.h | -rw-r--r-- | 43.1 KB |
actbl2.h | -rw-r--r-- | 57.1 KB |
actbl3.h | -rw-r--r-- | 21.9 KB |
actypes.h | -rw-r--r-- | 41.3 KB |
acuuid.h | -rw-r--r-- | 3.4 KB |
apei.h | -rw-r--r-- | 1.3 KB |
battery.h | -rw-r--r-- | 594 bytes |
button.h | -rw-r--r-- | 401 bytes |
cppc_acpi.h | -rw-r--r-- | 4.2 KB |
ghes.h | -rw-r--r-- | 3.6 KB |
hed.h | -rw-r--r-- | 370 bytes |
nfit.h | -rw-r--r-- | 351 bytes |
pcc.h | -rw-r--r-- | 651 bytes |
pdc_intel.h | -rw-r--r-- | 1.0 KB |
processor.h | -rw-r--r-- | 11.7 KB |
reboot.h | -rw-r--r-- | 201 bytes |
video.h | -rw-r--r-- | 2.8 KB |
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