Commit adc2ca50 authored by Mike Gerdts's avatar Mike Gerdts Committed by Jim Harris
Browse files

scripts: gdb needs a pretty printer for spinlocks 



In debug builds, SPDK spinlocks will have stack traces that track where
they were allocated, last locked, and last unlocked. This adds gdb
pretty printers to make that information easily visible. See the updates
in doc/gdb_macros.md for details.

Signed-off-by: default avatarMike Gerdts <mgerdts@nvidia.com>
Change-Id: I4f903c588d9384c4005eec01348fa5c2d3cab5db
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/16000


Reviewed-by: default avatarJim Harris <james.r.harris@intel.com>
Tested-by: default avatarSPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: default avatarShuhei Matsumoto <smatsumoto@nvidia.com>
parent 531258aa

doc/gdb_macros.md

+48 −0
Original line number Diff line number Diff line
@@ -125,6 +125,54 @@ nqn "nqn.2016-06.io.spdk.umgmt:cnode1", '\000' <repeats 191 times> 
ID 1

~~~



Printing SPDK spinlocks:



In this example, the spinlock has been initialized and locked but has never been unlocked.

After it is unlocked the first time the last unlocked stack will be present and the

`Locked by spdk_thread` line will say `not locked`.



~~~{.sh}

Breakpoint 2, spdk_spin_unlock (sspin=0x655110 <g_bdev_mgr+80>) at thread.c:2915

2915            struct spdk_thread *thread = spdk_get_thread();

(gdb) print *sspin

$2 = struct spdk_spinlock:

  Locked by spdk_thread: 0x658080

  Initialized at:

     0x43e677 <spdk_spin_init+213> thread.c:2878

     0x404feb <_bdev_init+16> /build/spdk/spdk-review-public/lib/bdev/bdev.c:116

     0x44483d <__libc_csu_init+77>

     0x7ffff62c9d18 <__libc_start_main+120>

     0x40268e <_start+46>

  Last locked at:

     0x43e936 <spdk_spin_lock+436> thread.c:2909

     0x40ca9c <bdev_name_add+129> /build/spdk/spdk-review-public/lib/bdev/bdev.c:3855

     0x411a3c <bdev_register+641> /build/spdk/spdk-review-public/lib/bdev/bdev.c:6660

     0x412e1e <spdk_bdev_register+24> /build/spdk/spdk-review-public/lib/bdev/bdev.c:7171

     0x417895 <num_blocks_test+119> bdev_ut.c:878

     0x7ffff7bc38cb <run_single_test.constprop+379>

     0x7ffff7bc3b61 <run_single_suite.constprop+433>

     0x7ffff7bc3f76 <CU_run_all_tests+118>

     0x43351f <main+1439> bdev_ut.c:6295

     0x7ffff62c9d85 <__libc_start_main+229>

     0x40268e <_start+46>

  Last unlocked at:

~~~



Print a single spinlock stack:



~~~{.sh}

(gdb) print sspin->internal.lock_stack

$1 = struct sspin_stack:

 0x40c6a1 <spdk_spin_lock+436> /build/spdk/spdk-review-public/lib/thread/thread.c:2909

 0x413f48 <spdk_spin+552> thread_ut.c:1831

 0x7ffff7bc38cb <run_single_test.constprop+379>

 0x7ffff7bc3b61 <run_single_suite.constprop+433>

 0x7ffff7bc3f76 <CU_run_all_tests+118>

 0x4148fa <main+547> thread_ut.c:1948

 0x7ffff62c9d85 <__libc_start_main+229>

 0x40248e <_start+46>

~~~



## Loading The gdb Macros



Copy the gdb macros to the host where you are about to debug.

scripts/gdb_macros.py

+68 −0
Original line number Diff line number Diff line
@@ -4,6 +4,7 @@ 
#



import gdb

import gdb.printing





class SpdkTailqList(object):
@@ -307,6 +308,64 @@ class spdk_print_threads(SpdkPrintCommand): 
        super(spdk_print_threads, self).__init__(name, threads)





class SpdkSpinlockStackPrinter(object):



    def __init__(self, val):

        self.val = val



    def to_array(self):

        ret = []

        count = self.val['depth']

        for i in range(count):

            line = ''

            addr = self.val['addrs'][i]

            line += ' ' + str(addr)

            # Source and line (sal) only exists for objects with debug info

            sal = gdb.find_pc_line(int(addr))

            try:

                line += ' ' + str(sal.symtab.filename)

                line += ':' + str(sal.line)

            except AttributeError as e:

                pass

            ret.append(line)

        return ret



    def to_string(self):

        return 'struct sspin_stack:\n' + '\n'.join(self.to_array())



    def display_hint(self):

        return 'struct sspin_stack'





class SpdkSpinlockPrinter(object):



    def __init__(self, val):

        self.val = val



    def to_string(self):

        thread = self.val['thread']

        internal = self.val['internal']

        s = 'struct spdk_spinlock:'

        s += '\n  Locked by spdk_thread: '

        if thread == 0:

            s += 'not locked'

        else:

            s += str(thread)

        if internal != 0:

            stacks = [

                ['Initialized', 'init_stack'],

                ['Last locked', 'lock_stack'],

                ['Last unlocked', 'unlock_stack']]

            for stack in stacks:

                s += '\n  ' + stack[0] + ' at:\n    '

                frames = SpdkSpinlockStackPrinter(internal[stack[1]])

                s += '\n    '.join(frames.to_array())

        return s



    def display_hint(self):

        return 'struct spdk_spinlock'





class spdk_load_macros(gdb.Command):



    def __init__(self):
@@ -316,12 +375,21 @@ class spdk_load_macros(gdb.Command): 
                             True)

        self.loaded = False



    def load_pretty_printers(self):

        pp = gdb.printing.RegexpCollectionPrettyPrinter("spdk_library")

        pp.add_printer('sspin_stack', '^sspin_stack$',

                       SpdkSpinlockStackPrinter)

        pp.add_printer('spdk_spinlock', '^spdk_spinlock$', SpdkSpinlockPrinter)

        gdb.printing.register_pretty_printer(gdb.current_objfile(), pp)



    def invoke(self, arg, from_tty):

        if arg == '--reload':

            print('Reloading spdk information')

            reload = True

        else:

            reload = False

            # These can only load once

            self.load_pretty_printers()



        if self.loaded and not reload:

            return