Re: BUG() in 2.4: sg direct IO + exit()

Douglas Gilbert
2004-03-24T12:57:06Z

Tony Battersby wrote:
> The following BUG() is triggered in 2.4.x when a program calls exit()
> immediately after sending a SCSI command that uses direct IO:
>
> kernel BUG at page_alloc.c:98!
> invalid operand: 0000
> sg sym53c8xx_2 e1000
> CPU: 0
> EIP: 0010:[<c0133d22>] Not tainted
> EFLAGS: 00010202
> EIP is at __free_pages_ok+0x32/0x2b0 [kernel]
> eax: 00000001 ebx: c12aceb0 ecx: c12aceb0 edx: 00000000
> esi: 00000000 edi: 00000000 ebp: 00000001 esp: c02bbe94
> ds: 0018 es: 0018 ss: 0018
> Process swapper (pid: 0, stackpage=c02bb000)
> Stack: cfefc640 cfdf2de8 cfbe93c0 cfefc600 00000001 00000000 cfefc600
> c12aceb0
> cf926fa0 00000000 cfb8b040 c0127cb0 cfb8b04c cfb8b04c cfb8b000
> d0885db6
> cf926fa0 00000000 cfb8b040 d0885cc9 cfb8b04c 00000001 cfd08680
> cfd086c8
> Call Trace:
> [<c0127cb0>] unmap_kiobuf+0x30/0x50 [kernel]
> [<d0885db6>] sg_unmap_and+0x26/0x50 [sg]
> [<d0885cc9>] sg_finish_rem_req+0x39/0x70 [sg]
> [<d0885451>] sg_cmd_done_bh+0x281/0x380 [sg]
> [<c01ab65a>] scsi_finish_command+0xda/0xe0 [kernel]
> [<c01ab380>] scsi_bottom_half_handler+0xc0/0x230 [kernel]
> [<c011dacb>] bh_action+0x4b/0x90 [kernel]
> [<c011d971>] tasklet_hi_action+0x61/0xa0 [kernel]
> [<c011d6fb>] do_softirq+0x6b/0xd0 [kernel]
> [<c0108baf>] do_IRQ+0xdf/0xf0 [kernel]
> [<c01052c0>] default_idle+0x0/0x40 [kernel]
> [<c01052c0>] default_idle+0x0/0x40 [kernel]
> [<c010b388>] call_do_IRQ+0x5/0xd [kernel]
> [<c01052c0>] default_idle+0x0/0x40 [kernel]
> [<c01052c0>] default_idle+0x0/0x40 [kernel]
> [<c01052ec>] default_idle+0x2c/0x40 [kernel]
> [<c0105372>] cpu_idle+0x52/0x70 [kernel]
> [<c0105000>] stext+0x0/0x50 [kernel]
>
> Code: 0f 0b 62 00 ab 04 23 c0 89 d8 e8 2f ed ff ff 8b 7b 28 85 ff
> <0>Kernel panic: Aiee, killing interrupt handler!
> In interrupt handler - not syncing
>
> The following program reproduces the problem:
>
> #include <stdlib.h>
> #include <stdio.h>
> #include <string.h>
> #include <unistd.h>
> #include <scsi/sg.h>
> #include <limits.h>
> #include <sys/types.h>
> #include <sys/stat.h>
> #include <fcntl.h>
>
> unsigned char mode_sense_cdb[] = { 0x1a, 0x00, 0x3f, 0x00, 0xff, 0x00 };
>
> int main(int argc, char *argv[])
> {
> int fd;
> unsigned char sense_data[256];
> unsigned char buf[256];
> sg_io_hdr_t io;
>
> fd = open("/dev/sg0", O_RDWR);
> if (fd == -1) {
> perror("open(/dev/sg0)");
> exit(1);
> }
>
> memset(&io, 0, sizeof(sg_io_hdr_t));
> io.interface_id = 'S';
> io.timeout = UINT_MAX;
> io.flags = SG_FLAG_DIRECT_IO;
> io.sbp = sense_data;
> io.mx_sb_len = 0xff;
> io.cmdp = mode_sense_cdb;
> io.cmd_len = 6;
> io.dxfer_direction = SG_DXFER_FROM_DEV;
> io.dxferp = buf;
> io.dxfer_len = 0xff;
> write(fd, &io, sizeof(sg_io_hdr_t));
>
> return 0;
> }
>
> Just compile, echo 1 > /proc/scsi/sg/allow_dio, and run. The SCSI
> device that I am using is a tape drive, but it shouldn't matter.
>
> I have tested this with 2.4.21+kksymoops and 2.4.26-pre5+kksymoops with
> the same results. The above stack trace is from 2.4.26-pre5. I haven't
> tried 2.6.
>
> I am running a SMP kernel on a UP Intel P4 with 256 MB RAM. The test
> machine does not have any swap space configured (swapoff -a).

Tony,
It is not causing an oops when I try with scsi_debug and lk 2.6.5-rc2.
Neither is there a problem with a Suse 9 stock SMP kernel
(2.4.21-99-smp4G) on an old dual celeron (A-bit mb) box with a
Sony SDT-7000 tape drive on /dev/sg0.

I'll keep looking. The oops suggests that the memory is not being
locked down (as you are probably aware).

Doug Gilbert