If I leave the system in the debugger console overnight with all the processors suspended for about 8 hours, then type go, the following bug shows up during file I/O. This particular bug showed up while using git to update some branches. I have only seen this bug once and I attempted to reproduce it to get a trace dump but have not been able to trigger it again. The NULL pointer is RDI set to NULL while trying to obtain a lock. (2)> .z grab_journal ffffffffa00bb740 t jbd2_journal_grab_journal_head [jbd2] (2)> u ffffffffa00bb740 jbd2|jbd2_journal_grab_journal_head: 0xffffffffa00bb740 0F1F440000 nop DWORD PTR [rax+rax]=0x0 0xffffffffa00bb745 55 push rbp 0xffffffffa00bb746 4889E5 mov rbp,rsp <<<<<<<<<<<< Crashes here with RDI set to NULL 0xffffffffa00bb749 F00FBA2F18 lock bts DWORD PTR [rdi]=0x0,0x18 <<<<<<<<<<<< 0xffffffffa00bb74e 7219 jb jbd2_journal_grab_journal_head+0x29 (0xffffffffa00bb769) (down) 0xffffffffa00bb750 488B07 mov rax,QWORD PTR [rdi]=0x0 0xffffffffa00bb753 A900000200 test eax,0x20000 0xffffffffa00bb758 741D je jbd2_journal_grab_journal_head+0x37 (0xffffffffa00bb777) (down) 0xffffffffa00bb75a 488B4740 mov rax,QWORD PTR [rdi+64]=0x0 0xffffffffa00bb75e 83400801 add DWORD PTR [rax+8]=0x0,0x1 0xffffffffa00bb762 F0806703FE lock and BYTE PTR [rdi+3]=0x00,0xfe 0xffffffffa00bb767 5D pop rbp 0xffffffffa00bb768 C3 ret 0xffffffffa00bb769 F390 pause 0xffffffffa00bb76b 488B07 mov rax,QWORD PTR [rdi]=0x0 0xffffffffa00bb76e A900000001 test eax,0x1000000 0xffffffffa00bb773 75F4 jne jbd2_journal_grab_journal_head+0x29 (0xffffffffa00bb769) (up) 0xffffffffa00bb775 EBD2 jmp jbd2_journal_grab_journal_head+0x9 (0xffffffffa00bb749) (up) 0xffffffffa00bb777 31C0 xor eax,eax The backtrace showed this function being called from the swapper thread when the crash occurred. It's damn hard to reproduce. If I see it again, I'll get you a better trace. Jeff -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
