linux-kernel - Re: [PATCH v2 01/20] rv/rvgen: introduce AutomataError exception class

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Message-ID: <aYT0ZasHDLVLCMTU@fedora>
Date: Thu, 5 Feb 2026 16:51:08 -0300
From: Wander Lairson Costa <wander@...hat.com>
To: Gabriele Monaco <gmonaco@...hat.com>
Cc: Steven Rostedt <rostedt@...dmis.org>, Nam Cao <namcao@...utronix.de>, 
	"open list:RUNTIME VERIFICATION (RV)" <linux-trace-kernel@...r.kernel.org>, open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 01/20] rv/rvgen: introduce AutomataError exception
 class

On Thu, Feb 05, 2026 at 01:08:41PM +0100, Gabriele Monaco wrote:
> On Wed, 2026-02-04 at 11:42 -0300, Wander Lairson Costa wrote:
> > Replace the generic except Exception block with a custom AutomataError
> > class that inherits from Exception. This provides more precise exception
> > handling for automata parsing and validation errors while avoiding
> > overly broad exception catches that could mask programming errors like
> > SyntaxError or TypeError.
> > 
> > The AutomataError class is raised when DOT file processing fails due to
> > invalid format, I/O errors, or malformed automaton definitions. The
> > main entry point catches this specific exception and provides a
> > user-friendly error message to stderr before exiting.
> > 
> > Signed-off-by: Wander Lairson Costa <wander@...hat.com>
> [...]
> > ---
> > @@ -45,8 +52,8 @@ class Automata:
> >          dot_lines = []
> >          try:
> >              dot_file = open(self.__dot_path)
> > -        except:
> > -            raise Exception("Cannot open the file: %s" % self.__dot_path)
> > +        except OSError as exc:
> > +            raise AutomataError(f"Cannot open the file: {self.__dot_path}")
> > from exc
> > 
> 
> You probably don't want to mask all OSError in main.py and allow only this one.
> I think it's alright to keep a simpler message for wrong model file (also LTL!),
> while throwing a splat in other cases (e.g. missing templates).
> 
> But wouldn't it be better to show the error message of the OSError? 99% of the
> time it's going to be ENOENT, but could also be some EPERM or who knows what.
> I'm fine keeping AutomataError here but would at least propagate the error
> message.
> 
> Or keep it simple and catch all OSError as well, this one included.

Now that we catch OSError in the main, it makes sense to remove the
try/except clause around open().

> 
> Thanks,
> Gabriele
> 
> >  
> >          dot_lines = dot_file.read().splitlines()
> >          dot_file.close()
> > @@ -55,7 +62,7 @@ class Automata:
> >          line = dot_lines[cursor].split()
> >  
> >          if (line[0] != "digraph") and (line[1] != "state_automaton"):
> > -            raise Exception("Not a valid .dot format: %s" % self.__dot_path)
> > +            raise AutomataError("Not a valid .dot format: %s" %
> > self.__dot_path)
> >          else:
> >              cursor += 1
> >          return dot_lines
> > diff --git a/tools/verification/rvgen/rvgen/dot2c.py
> > b/tools/verification/rvgen/rvgen/dot2c.py
> > index 06a26bf15a7e9..74147ae2942f9 100644
> > --- a/tools/verification/rvgen/rvgen/dot2c.py
> > +++ b/tools/verification/rvgen/rvgen/dot2c.py
> > @@ -13,7 +13,7 @@
> >  # For further information, see:
> >  #   Documentation/trace/rv/deterministic_automata.rst
> >  
> > -from .automata import Automata
> > +from .automata import Automata, AutomataError
> >  
> >  class Dot2c(Automata):
> >      enum_suffix = ""
> > @@ -71,7 +71,7 @@ class Dot2c(Automata):
> >              min_type = "unsigned int"
> >  
> >          if self.states.__len__() > 1000000:
> > -            raise Exception("Too many states: %d" % self.states.__len__())
> > +            raise AutomataError("Too many states: %d" %
> > self.states.__len__())
> >  
> >          return min_type
> >  
> > diff --git a/tools/verification/rvgen/rvgen/generator.py
> > b/tools/verification/rvgen/rvgen/generator.py
> > index 3441385c11770..a7bee6b1ea70c 100644
> > --- a/tools/verification/rvgen/rvgen/generator.py
> > +++ b/tools/verification/rvgen/rvgen/generator.py
> > @@ -51,10 +51,7 @@ class RVGenerator:
> >          raise FileNotFoundError("Could not find the rv directory, do you have
> > the kernel source installed?")
> >  
> >      def _read_file(self, path):
> > -        try:
> > -            fd = open(path, 'r')
> > -        except OSError:
> > -            raise Exception("Cannot open the file: %s" % path)
> > +        fd = open(path, 'r')
> >  
> >          content = fd.read()
> >  
> > @@ -65,7 +62,7 @@ class RVGenerator:
> >          try:
> >              path = os.path.join(self.abs_template_dir, file)
> >              return self._read_file(path)
> > -        except Exception:
> > +        except OSError:
> >              # Specific template file not found. Try the generic template file
> > in the template/
> >              # directory, which is one level up
> >              path = os.path.join(self.abs_template_dir, "..", file)
>