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    Subject[PATCH v4 0/8] Function tracing support for pstore
    Hi all,

    In v4:
    - A few cosmetic changes in func_set_flag(), as suggested by Steven
    Rostedt. Firstly, in the patch that adds pstore option, I use
    'else if' for the new bit (it keeps changes minimal), but then there
    is a new separate patch (the last in the series) that converts the
    whole thing into a switch construction.

    In v3:
    - Make traces versioned, as suggested by Steven, Tony and Colin. (The
    version tag is stored in the PRZ signature, see the last patch for
    the implementation details).
    - Add Steven's Ack on the first patch.

    In v2:
    - Do not introduce a separate 'persistent' tracer, but introduce an
    option to the existing 'function' tracer.

    Rationale for this patch set:

    With this support kernel can save functions call chain log into a
    persistent ram buffer that can be decoded and dumped after reboot
    through pstore filesystem. It can be used to determine what function
    was last called before a hang or an unexpected reset (caused by, for
    example, a buggy driver that abuses HW).

    Here's a "nano howto", to get the idea:

    # mount -t debugfs debugfs /sys/kernel/debug/
    # cd /sys/kernel/debug/tracing
    # echo function > current_tracer
    # echo 1 > options/func_pstore
    # reboot -f
    [...]
    # mount -t pstore pstore /mnt/
    # tail /mnt/ftrace-ramoops
    0 ffffffff8101ea64 ffffffff8101bcda native_apic_mem_read <- disconnect_bsp_APIC+0x6a/0xc0
    0 ffffffff8101ea44 ffffffff8101bcf6 native_apic_mem_write <- disconnect_bsp_APIC+0x86/0xc0
    0 ffffffff81020084 ffffffff8101a4b5 hpet_disable <- native_machine_shutdown+0x75/0x90
    0 ffffffff81005f94 ffffffff8101a4bb iommu_shutdown_noop <- native_machine_shutdown+0x7b/0x90
    0 ffffffff8101a6a1 ffffffff8101a437 native_machine_emergency_restart <- native_machine_restart+0x37/0x40
    0 ffffffff811f9876 ffffffff8101a73a acpi_reboot <- native_machine_emergency_restart+0xaa/0x1e0
    0 ffffffff8101a514 ffffffff8101a772 mach_reboot_fixups <- native_machine_emergency_restart+0xe2/0x1e0
    0 ffffffff811d9c54 ffffffff8101a7a0 __const_udelay <- native_machine_emergency_restart+0x110/0x1e0
    0 ffffffff811d9c34 ffffffff811d9c80 __delay <- __const_udelay+0x30/0x40
    0 ffffffff811d9d14 ffffffff811d9c3f delay_tsc <- __delay+0xf/0x20

    Mostly the code comes from trace_persistent.c driver found in the
    Android git tree, written by Colin Cross <ccross@android.com>
    (according to sign-off history). I reworked the driver a little bit,
    and ported it to pstore subsystem.

    ---
    Documentation/ramoops.txt | 25 +++++++++
    fs/pstore/Kconfig | 13 +++++
    fs/pstore/Makefile | 1 +
    fs/pstore/ftrace.c | 35 +++++++++++++
    fs/pstore/inode.c | 111 ++++++++++++++++++++++++++++++++++++++--
    fs/pstore/internal.h | 43 ++++++++++++++++
    fs/pstore/platform.c | 12 ++++-
    fs/pstore/ram.c | 65 +++++++++++++++++------
    fs/pstore/ram_core.c | 12 +++--
    include/linux/pstore.h | 13 +++++
    include/linux/pstore_ram.h | 3 +-
    kernel/trace/trace.c | 7 +--
    kernel/trace/trace_functions.c | 36 +++++++++----
    13 files changed, 337 insertions(+), 39 deletions(-)

    --
    Anton Vorontsov
    Email: cbouatmailru@gmail.com


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