simark

$ lttng create
$ lttng enable-event -u -a
$ lttng start
$ ./memcached

    Generate some traffic. There are some printfs that indicate that both tracepoints should be hit.

$ lttng stop
$ lttng destroy

simark

// Enlever prix/quantités usagé
db.pieces.update({_id: {$exists: true}}, { $rename: {'prixneuf':'prix', 'quantiteneuf':'quantite'}, $unset: {'quantiteusage': true, 'prixusage': true} }, {multi: true})

// Trouver factures problématiques
db.factures.find({ 'pieces': {$elemMatch: { 'quantiteusage': {$exists: true}, 'quantiteneuf': {$exists: true}   }} })

simark

class EnterBreakpoint(gdb.Breakpoint):
	def __init__(self):
		super(EnterBreakpoint, self).__init__("hopefully_notinlined")
		
	def stop(self):
		FinishBp()

class FinishBp(gdb.FinishBreakpoint):
    def stop(self):
		print("I am here")

simark

Les étapes entre le moment où on tappe "ls -1 *.txt" suivi de "enter" dans bash et le moment où on peut lire la liste des fichiers à l'écran. C'est très rapide, mais il s'en passe des choses...

$ ls -l undossier *.txt
-rw-rw-r-- 1 simark simark    0 Mar  9 22:17 bob.txt
-rw-rw-r-- 1 simark simark    0 Mar  9 22:17 machin.txt
-rw-rw-r-- 1 simark simark    0 Mar  9 22:17 truc.txt

undossier:
total 0
-rw-rw-r-- 1 simark simark 0 Mar  9 22:29 unfichier

simark

def iso_to_utf(m):
	m.Lock()
	try:
		m.description.decode('utf-8')
	except UnicodeDecodeError as e:
		# La description n'est pas en utf-8, on la transforme.
		m.description = m.description.decode('iso-8859-1').encode()
		m.Save()

simark

* Permissions and scope (system-global vs user-global)

Use case:
A user would like to debug its CGI web application written in C with
GDB. It is hosted on a shared server, where Apache runs as www-data.
When a request comes in, Apache forks, does some some suid magic to run
the CGI program as the user and the program finishes. It can be
difficult to debug this, since the user can't attach a debugger to
Apache. He can use the trick of putting a sleep or infinite loop in its
program, but that is always inconvenient.

simark

def stacktraces():
    code = []
    for threadId, stack in sys._current_frames().items():
        code.append("\n# ThreadID: %s" % threadId)
        for filename, lineno, name, line in traceback.extract_stack(stack):
            code.append('File: "%s", line %d, in %s' %
                        (filename, lineno, name))
            if line:
                code.append("  %s" % (line.strip()))

simark

all: libtruc.so app

app: app.o
	gcc -o app app.o -ldl -llttng-ust
app.o: app.c
	gcc -c app.c -g3 -O0 -Wall


libtruc.so: truc.o tracepoints.o
	gcc -shared -o libtruc.so truc.o tracepoints.o -llttng-ust

simark

Hello

simark

# Terminology

Throughout this document, "host" refers to the build machine and "target"
refers to the machine where OLA will run.  Note that this does not match
Autoconf's terminology, where "host" means the machine where things will run.

During the process, we will need to build some things that will run on the host
machine, and others that will run on the target machine.  We will therefore
work with two separate terminals, one set up to build things for each.  I'll
refer to those as "host terminal" and "target terminal".