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s390: Remove GENERIC_LOCKBREAK Kconfig option

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s390 selects GENERIC_LOCKBREAK if PREEMPT is enabled. Reason is a historic
18 years old commit [1] which fixed a compile error for PREEMPT enabled
kernels. Back than only PREEMPT_NONE and PREEMPT_VOLUNTARY kernels were
considered to be important for s390. PREEMPT should "just work".

However, since recently PREEMPT is always enabled [2], which also causes
GENERIC_LOCKBREAK to be always enabled. For some workloads this leads to
massive performance degradation; e.g. a simple kernel compile on machines
with many CPUs may take up to four times longer.

To fix this just remove the GENERIC_LOCKBREAK from s390's Kconfig, since
the compile error from 18 years ago does not exist anymore.

[1] commit b6b40c532a ("[S390] Define GENERIC_LOCKBREAK.")
[2] commit 7dadeaa6e8 ("sched: Further restrict the preemption modes")

Cc: stable@vger.kernel.org
Reported-by: Massimiliano Pellizzer <massimiliano.pellizzer@canonical.com>
Reviewed-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
This commit is contained in:
Heiko Carstens 2026-06-05 17:32:06 +02:00 • committed by Alexander Gordeev
commit 1f57f68c4d
1 changed files with 0 additions and 3 deletions
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arch/s390/Kconfig
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@ -29,9 +29,6 @@ config GENERIC_BUG
config GENERIC_BUG_RELATIVE_POINTERS
def_bool y
config GENERIC_LOCKBREAK
def_bool y if PREEMPTION
config AUDIT_ARCH
def_bool y