mips qemu test failures in -next due to "kthread: Fix use-after-free if kthread fork fails"

[Guenter Roeck]

Hi,

my qemu testis of mips images are failing in -next. Symptom is a hang during
boot; see http://kerneltests.org/builders/qemu-mips-next for some examples.

I bisected the problem in next-20170526. It points to commit 4d6501dce079c
("kthread: Fix use-after-free if kthread fork fails"). Reverting that patch
fixes the problem.

Bisect log is attached.

Guenter

---
# bad: [494a19b0aa3c905b6c5221f49058526896b06a23] Add linux-next specific files for 20170526
# good: [08332893e37af6ae779367e78e444f8f9571511d] Linux 4.12-rc2
git bisect start 'HEAD' 'v4.12-rc2'
# good: [61f91dc3a7c15bdc06e746b0fa30a2b125bd41b6] Merge remote-tracking branch 'drm/drm-next'
git bisect good 61f91dc3a7c15bdc06e746b0fa30a2b125bd41b6
# bad: [854cfdd6fc9298018f6625d5e495405b2687b13c] Merge remote-tracking branch 'tip/auto-latest'
git bisect bad 854cfdd6fc9298018f6625d5e495405b2687b13c
# good: [bb4b4365c7a19d593d190ec6a380a7835b20e3fc] Merge remote-tracking branch 'sound/for-next'
git bisect good bb4b4365c7a19d593d190ec6a380a7835b20e3fc
# good: [830aade0f6121bf1bfa6504aa588b23469694803] Merge remote-tracking branch 'battery/for-next'
git bisect good 830aade0f6121bf1bfa6504aa588b23469694803
# bad: [0f90e8b13c713120ae0d2485533e5acf956f8321] Merge branch 'x86/boot'
git bisect bad 0f90e8b13c713120ae0d2485533e5acf956f8321
# good: [d04e31a23c3c828456cb5613f391ce4ac4e5765f] cpufreq/pasemi: Adjust system_state check
git bisect good d04e31a23c3c828456cb5613f391ce4ac4e5765f
# bad: [a451941cac2792181be56857e70233cbb9957cd2] Merge branch 'perf/urgent'
git bisect bad a451941cac2792181be56857e70233cbb9957cd2
# bad: [2c510368365cd0ce0c48c3f97a7048dc07ccd94a] Merge branch 'locking/urgent'
git bisect bad 2c510368365cd0ce0c48c3f97a7048dc07ccd94a
# good: [b9de5068b2d7c22de1bb89d62a7119a6b8dff88f] x86/ioapic: Remove unused IO_APIC_irq_trigger() function
git bisect good b9de5068b2d7c22de1bb89d62a7119a6b8dff88f
# bad: [79824ccf1691d0b8d4ef83d5d212ba0b31d8081e] Merge branch 'core/urgent'
git bisect bad 79824ccf1691d0b8d4ef83d5d212ba0b31d8081e
# bad: [4d6501dce079c1eb6bf0b1d8f528a5e81770109e] kthread: Fix use-after-free if kthread fork fails
git bisect bad 4d6501dce079c1eb6bf0b1d8f528a5e81770109e
# first bad commit: [4d6501dce079c1eb6bf0b1d8f528a5e81770109e] kthread: Fix use-after-free if kthread fork fails