Am 04.05.21 um 17:55 schrieb Simon Marchi: > On 2021-05-04 11:35 a.m., Borislav Petkov wrote: >> On Tue, May 04, 2021 at 10:39:23AM +0200, Peter Zijlstra wrote: >>> Anybody on toolchains that can help get GDB fixed? >> >> In the meantime, Tom is looking at fixing this, in case people wanna try >> gdb patches or give him a test case or so... >> >> https://sourceware.org/bugzilla/show_bug.cgi?id=27822 > > Yes, please provide reproducing steps in that bug. Unlike what was said > in this thread, some people do work on gdb and are willing to fix > things, but they can only do so if they know about the problem. See https://lore.kernel.org/io-uring/0375b37f-2e1e-7999-53b8-c567422aa181@xxxxxxxxx/ and https://lore.kernel.org/io-uring/20210411152705.2448053-1-metze@xxxxxxxxx/T/#m461f280e8c3d32a49bc7da7bb5e214e90d97cf65 The question is why does inferior_ptid doesn't represent the thread that was specified by 'gdb --pid PIDVAL' https://www.samba.org/~metze/strace-uring-fail.txt used "gdb --pid 1396" and does the following ptrace calls: # grep ptrace strace-uring-fail.txt > 18:46:35.319925 ptrace(PTRACE_ATTACH, 1396) = 0 <0.000048> > 18:46:35.321622 ptrace(PTRACE_ATTACH, 1397) = 0 <0.000059> > 18:46:35.322813 ptrace(PTRACE_ATTACH, 1398) = 0 <0.003052> > 18:46:35.327287 ptrace(PTRACE_ATTACH, 1399) = 0 <0.000028> > 18:46:35.334920 ptrace(PTRACE_GETREGS, 1396, NULL, 0x7ffed6173ea0) = 0 <0.000067> > 18:46:35.341506 ptrace(PTRACE_SETOPTIONS, 1410, NULL, PTRACE_O_TRACESYSGOOD) = 0 <0.000056> > 18:46:35.341681 ptrace(PTRACE_SETOPTIONS, 1410, NULL, PTRACE_O_TRACEFORK) = 0 <0.000051> > 18:46:35.341816 ptrace(PTRACE_SETOPTIONS, 1410, NULL, PTRACE_O_TRACEFORK|PTRACE_O_TRACEVFORKDONE) = 0 <0.000054> > 18:46:35.341957 ptrace(PTRACE_CONT, 1410, NULL, 0) = 0 <0.000056> > 18:46:35.345568 ptrace(PTRACE_GETEVENTMSG, 1410, NULL, [1411]) = 0 <0.000081> > 18:46:35.350541 ptrace(PTRACE_SETOPTIONS, 1410, NULL, PTRACE_O_EXITKILL) = 0 <0.000019> > 18:46:35.354010 ptrace(PTRACE_SETOPTIONS, 1397, NULL, PTRACE_O_TRACESYSGOOD|PTRACE_O_TRACEFORK|PTRACE_O_TRACEVFORK|PTRACE_O_TRACECLONE|PTRACE_O_TRACEEXEC|PTRACE_O_TRACEVFORKDONE) = 0 <0.000019> > 18:46:35.415730 ptrace(PTRACE_SETOPTIONS, 1396, NULL, PTRACE_O_TRACESYSGOOD|PTRACE_O_TRACEFORK|PTRACE_O_TRACEVFORK|PTRACE_O_TRACECLONE|PTRACE_O_TRACEEXEC|PTRACE_O_TRACEVFORKDONE) = 0 <0.000076> > 18:46:35.421076 ptrace(PTRACE_GETREGS, 1412, NULL, 0x7ffed6174980) = 0 <0.000088> > 18:46:35.429498 ptrace(PTRACE_PEEKUSER, 1397, 8*CS, [NULL]) = 0 <0.000022> > 18:46:35.429632 ptrace(PTRACE_PEEKUSER, 1397, 8*SS + 24, [NULL]) = 0 <0.000019> > 18:46:35.429732 ptrace(PTRACE_GETREGSET, 1397, NT_X86_XSTATE, [{iov_base=0x7ffed6174780, iov_len=576}]) = 0 <0.000030> > 18:46:35.435507 ptrace(PTRACE_GETREGS, 1397, NULL, 0x7ffed6173cb0) = 0 <0.000019> > 18:46:35.445877 ptrace(PTRACE_PEEKTEXT, 1397, 0x56357e99de00, [0x7f49d572b160]) = 0 <0.000057> > 18:46:35.446043 ptrace(PTRACE_PEEKTEXT, 1397, 0x7f49d572b168, [0x7f49d572b190]) = 0 <0.000049> > 18:46:35.447192 ptrace(PTRACE_PEEKTEXT, 1397, 0x7f49d572bbf0, [0x64762d78756e696c]) = 0 <0.000060> > 18:46:35.447368 ptrace(PTRACE_PEEKTEXT, 1397, 0x7f49d572bbf0, [0x64762d78756e696c]) = 0 <0.000075> > 18:46:35.447571 ptrace(PTRACE_PEEKTEXT, 1397, 0x7f49d572bbf8, [0x312e6f732e6f73]) = 0 <0.000070> > 18:46:35.447762 ptrace(PTRACE_PEEKTEXT, 1397, 0x7f49d572bbf8, [0x312e6f732e6f73]) = 0 <0.000067> > 18:46:35.448658 ptrace(PTRACE_PEEKTEXT, 1397, 0x7f49d572be10, [0x3638782f62696c2f]) = 0 <0.000076> > 18:46:35.448917 ptrace(PTRACE_PEEKTEXT, 1397, 0x7f49d572be10, [0x3638782f62696c2f]) = 0 <0.000050> > 18:46:35.449051 ptrace(PTRACE_PEEKTEXT, 1397, 0x7f49d572be18, [0x756e696c2d34365f]) = 0 <0.000045> > 18:46:35.449173 ptrace(PTRACE_PEEKTEXT, 1397, 0x7f49d572be18, [0x756e696c2d34365f]) = 0 <0.000043> > 18:46:35.449292 ptrace(PTRACE_PEEKTEXT, 1397, 0x7f49d572be20, [0x696c2f756e672d78]) = 0 <0.000042> > 18:46:35.449414 ptrace(PTRACE_PEEKTEXT, 1397, 0x7f49d572be20, [0x696c2f756e672d78]) = 0 <0.000048> ptrace(PTRACE_GETREGS, 1396, ... looks expected to me, but starting with ptrace(PTRACE_PEEKUSER, 1397, 8*CS, [NULL]) (which triggers the actual problem) it's unexpected to me why 1397 is used instead of 1396. 1397 is the iou-mgr-1396 iothread. I hope that helps! metze
