https://bugzilla.wikimedia.org/show_bug.cgi?id=43034
Web browser: ---
Bug ID: 43034
Summary: Bombarding PHP with signals every 2 milliseconds
breaks things
Product: MediaWiki extensions
Version: master
Hardware: All
OS: All
Status: NEW
Severity: normal
Priority: Unprioritized
Component: Scribunto
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected]
Classification: Unclassified
Mobile Platform: ---
Created attachment 11496
--> https://bugzilla.wikimedia.org/attachment.cgi?id=11496&action=edit
Test script
(we don't have a separate product/component for LuaSandbox?)
The LuaSandbox PHP extension, when profiling is enabled, will bombard PHP with
SIGRT_7 every 2 milliseconds. This tends to randomly break important syscalls
as they get constantly interrupted.
For example, if PHP has allocated enough memory that a clone() system call
would take more than 2 milliseconds then it will never finish because it will
constantly get interrupted. The attached test program illustrates this; if you
have a particularly fast machine, you might have to increase the size of the
allocated string.
For another example, I noticed that the Scribunto unit tests would randomly die
when run using the LuaSandbox engine. That stopped once I fixed this bug. Not
entirely conclusive, but suggestive that something in PHP got an unexpected
EINTR and decided to kill the process.
If LuaSandbox is compiled with LUASANDBOX_PROFILER_USE_THREAD, this isn't a
problem because it uses a different mechanism for the profiling. But if you
really want to keep the possibility of using signals, it also seems to work to
block the signal (using sigprocmask) whenever in_lua is false.
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