intermittent lgwr hang situations

dear community,

I have intermittent lgwr hang issues on  a RAC one node (12.1.0.2. on RedHat 7.6) on ASM.

lgwr process hangs up to 80 seconds.

I had a strace session running in one case showing a gap of 30 seconds between io_submit and write call.

Example for a 30 second hang:

45487 12:56:22.188725 write(10, "\n", 1) = 1 <0.000015> | 00000  0a                                                .                |

45487 12:56:22.188811 io_submit(140107792158720, 2, [{data=0x7f6d631dd6c8, pwrite, fildes=256, str="\1\"\0\0\335-\2\0\354>\1\0\20\200\2546p\3\0\0\5\4\21\0F\330\371\332\1\0\0\1"..., nbytes=8192, offset=35556932096}, {data=0x7f6d63154dd8, pwrite, fildes=259, str="\1\"\0\0\335-\2\0\354>\1\0\20\200\2546p\3\0\0\5\4\21\0F\330\371\332\1\0\0\1"..., nbytes=8192, offset=411513371136}]) = 2 <0.000047>d6c8, res=8192, res2=0}], {600, 0}) = 2 <30.818347>

45487 12:56:53.007372 times(NULL)       = 541931600 <0.000010>

45487 12:56:53.007428 write(10, "\n*** 2019-05-10 12:56:53.007\n", 29) = 29 <0.000055>

| 00000  0a 2a 2a 2a 20 32 30 31  39 2d 30 35 2d 31 30 20  .*** 2019-05-10  |

| 00010  31 32 3a 35 36 3a 35 33  2e 30 30 37 0a           12:56:53.007.    |