Signals in Firefox

[David Teller]

Dear platformers,

What is our policy on using Unix signals on Firefox? I am currently
reviewing a patch by external contributors that involves inotify's
signal API, and I assume it's a bad idea, but I'd like to ask around
first before sending them back to the drawing board.

Cheers,
Yoric

[Nathan Froyd]

Post by David Teller
What is our policy on using Unix signals on Firefox? I am currently
reviewing a patch by external contributors that involves inotify's
signal API, and I assume it's a bad idea, but I'd like to ask around
first before sending them back to the drawing board.

I don't think we have a policy, per se; certainly we already have uses
of signals in the JS engine's wasm implementation and the Gecko
profiler. But in those cases, signals are basically the only way to
do what we want. If there were alternative ways to accomplish those
tasks besides signals, I think we would have avoided signals.

inotify looks like it has a file descriptor-based interface which
seems perfectly usable. Not being familiar with inotify beyond
reading http://man7.org/linux/man-pages/man7/inotify.7.html, is there
a reason to prefer the signal interface versus the file descriptor
interface? We use the standard gio/gtk event loop, so hooking up the
returned file descriptor from inotify_init should not be onerous.
widget/gtk/nsAppShell.cpp even contains some code to crib from:

https://searchfox.org/mozilla-central/source/widget/gtk/nsAppShell.cpp#275-281

-Nathan

[Mike Hommey]

Post by Nathan Froyd

Post by David Teller
What is our policy on using Unix signals on Firefox? I am currently
reviewing a patch by external contributors that involves inotify's
signal API, and I assume it's a bad idea, but I'd like to ask around
first before sending them back to the drawing board.

I don't think we have a policy, per se; certainly we already have uses
of signals in the JS engine's wasm implementation and the Gecko
profiler. But in those cases, signals are basically the only way to
do what we want. If there were alternative ways to accomplish those
tasks besides signals, I think we would have avoided signals.
inotify looks like it has a file descriptor-based interface which
seems perfectly usable. Not being familiar with inotify beyond
reading http://man7.org/linux/man-pages/man7/inotify.7.html, is there
a reason to prefer the signal interface versus the file descriptor
interface? We use the standard gio/gtk event loop, so hooking up the
returned file descriptor from inotify_init should not be onerous.
https://searchfox.org/mozilla-central/source/widget/gtk/nsAppShell.cpp#275-281

I'd go one step further. We use Gio from libglib, is there a reason not
to use the GFileMonitor API, which wraps inotify?

https://developer.gnome.org/gio/stable/GFileMonitor.html

Mike

[David Teller]

Thanks for the suggestions.

Given that they are on an academic deadline and they have already
implemented the feature using straight inotify and a monitor thread, I'd
favor a lesser refactoring with just removing the signals.

Cheers,
David

Post by Mike Hommey

Post by Nathan Froyd

Post by David Teller
What is our policy on using Unix signals on Firefox? I am currently
reviewing a patch by external contributors that involves inotify's
signal API, and I assume it's a bad idea, but I'd like to ask around
first before sending them back to the drawing board.

I don't think we have a policy, per se; certainly we already have uses
of signals in the JS engine's wasm implementation and the Gecko
profiler. But in those cases, signals are basically the only way to
do what we want. If there were alternative ways to accomplish those
tasks besides signals, I think we would have avoided signals.
inotify looks like it has a file descriptor-based interface which
seems perfectly usable. Not being familiar with inotify beyond
reading http://man7.org/linux/man-pages/man7/inotify.7.html, is there
a reason to prefer the signal interface versus the file descriptor
interface? We use the standard gio/gtk event loop, so hooking up the
returned file descriptor from inotify_init should not be onerous.
https://searchfox.org/mozilla-central/source/widget/gtk/nsAppShell.cpp#275-281

I'd go one step further. We use Gio from libglib, is there a reason not
to use the GFileMonitor API, which wraps inotify?
https://developer.gnome.org/gio/stable/GFileMonitor.html
Mike