[Lenovo P2 ROMs, Kernels, Recoveries, & Other Devel] rdanel88:
For those having battery drain issues or in general troubles with the battery duration, try to look at logcat or at the "top" shell command output.

If you have a "vfmService" process using a lot of CPU in top or the following kind of lines in the logcat you may suffer of the battery drain connected to faulty fingerprint.

Fatal signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0xc in tid 3075 (vfmService), pid 3055 (vfmService)

08-09 15:22:05.140 3084 3084 F DEBUG : *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***

08-09 15:22:05.140 3084 3084 F DEBUG : LineageOS Version: '17.1-20200809-NIGHTLY-kuntao'

08-09 15:22:05.140 3084 3084 F DEBUG : Build fingerprint: 'Lenovo/kuntao_row/P2a42:7.0/NRD90N/P2a42_S251_171107_ROW:user/release-keys'

08-09 15:22:05.140 3084 3084 F DEBUG : Revision: '0'

08-09 15:22:05.140 3084 3084 F DEBUG : ABI: 'arm64'

08-09 15:22:05.141 3084 3084 F DEBUG : Timestamp: 2020-08-09 15:22:05+0200

08-09 15:22:05.141 3084 3084 F DEBUG : pid: 3055, tid: 3075, name: vfmService >>> /vendor/bin/vfmService <<<

08-09 15:22:05.141 3084 3084 F DEBUG : uid: 1000

08-09 15:22:05.141 3084 3084 F DEBUG : signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0xc

08-09 15:22:05.141 3084 3084 F DEBUG : Cause: null pointer dereference

08-09 15:22:05.141 3084 3084 F DEBUG : x0 0000000000000003 x1 0000007e8d18f450 x2 0000000000000005 x3 0000000000000003

08-09 15:22:05.141 3084 3084 F DEBUG : x4 0000000000000000 x5 73ffffffffffffff x6 0000000080000000 x7 0000008000000000

08-09 15:22:05.141 3084 3084 F DEBUG : x8 9800c6c2172af40a x9 9800c6c2172af40a x10 0000007e8d18f5f0 x11 0000000000000011

08-09 15:22:05.141 3084 3084 F DEBUG : x12 0101010101010101 x13 0000000000000018 x14 0000000000000001 x15 000042256458bbd4

08-09 15:22:05.141 3084 3084 F DEBUG : x16 0000007e973b2640 x17 0000007e970bd150 x18 0000007e8c794000 x19 0000007e96a4c000

08-09 15:22:05.141 3084 3084 F DEBUG : x20 00000000000000ce x21 0000000000000000 x22 0000007e9536b000 x23 0000007e96a0bd90

08-09 15:22:05.141 3084 3084 F DEBUG : x24 0000000000000000 x25 0000007e8d18fd50 x26 0000007e9523e928 x27 0000007e9755a020

08-09 15:22:05.141 3084 3084 F DEBUG : x28 0000007e8d18fc40 x29 0000007e8d18fb60

08-09 15:22:05.141 3084 3084 F DEBUG : sp 0000007e8d18fb60 lr 0000007e952495ac pc 0000007e95249fc8

08-09 15:22:05.144 3084 3084 F DEBUG :

08-09 15:22:05.144 3084 3084 F DEBUG : backtrace:

08-09 15:22:05.144 3084 3084 F DEBUG : #00 pc 00000000000a7fc8 /vendor/lib64/libvalAuth.so (vfmExPerformNav+3252)

08-09 15:22:05.144 3084 3084 F DEBUG : #01 pc 000000000009bf5c /vendor/lib64/libvalAuth.so (vcs::CAPIHandlerVfm::NavStart(void*)+44)

08-09 15:22:05.144 3084 3084 F DEBUG : #02 pc 000000000006a9dc /vendor/bin/vfmService (vcs::CAPIHandlerServer::NavStart(void*)+32)

08-09 15:22:05.145 3084 3084 F DEBUG : #03 pc 000000000006d9a0 /vendor/bin/vfmService (vcs::CVcsServer::NavStart(void*)+32)

08-09 15:22:05.145 3084 3084 F DEBUG : #04 pc 000000000006a5e4 /vendor/bin/vfmService (vcs::CNavThread::NavStartHandler()+120)

08-09 15:22:05.145 3084 3084 F DEBUG : #05 pc 000000000006a634 /vendor/bin/vfmService (vcs::CNavThread::NavHandlerThread(void*)+24)

08-09 15:22:05.145 3084 3084 F DEBUG : #06 pc 00000000000e2390 /apex/com.android.runtime/lib64/bionic/libc.so (__pthread_start(void*)+36) (BuildId: bf14cf7a62d1f91755beddd4a937354d)

08-09 15:22:05.145 3084 3084 F DEBUG : #07 pc 0000000000083ab0 /apex/com.android.runtime/lib64/bionic/libc.so (__start_thread+64) (BuildId: bf14cf7a62d1f91755beddd4a937354d)

08-09 15:22:11.724 3091 3150 F libc : Fatal signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0xc in tid 3150 (vfmService), pid 3091 (vfmService)

if I'm not the only one affected by this problem I will fill a new bug report for LOS 17 as I did for LOS 16. For those interested, the workaround used for 16 is still valid for 17:

as root run the following shell command:
mount -o remount,rw /vendor
mv "/vendor/bin/hw/android.hardware.biometrics.fingerprint@2.0-service.kuntao" "/vendor/bin/hw/android.hardware.biometrics.fingerprint@2.0-service.kuntao2"