Bug 245618

Summary:	[Linux] No thread priority demoting through rtkit portal
Product:	WebKit	Reporter:	Philippe Normand <philn>
Component:	WPE WebKit	Assignee:	Nobody <webkit-unassigned>
Status:	RESOLVED INVALID
Severity:	Normal	CC:	bugs-noreply, cgarcia
Priority:	P2
Version:	WebKit Nightly Build
Hardware:	Unspecified
OS:	Unspecified

Description Philippe Normand 2022-09-24 06:43:52 PDT

I'm not sure if this is an issue or not... RealTimeThreads::promoteThreadToRealTime() has rtkit support. RealTimeThreads::demoteThreadFromRealTime() does not. When I run the WPE Debug tests after a while I see this in the journal:

Sep 24 14:37:50 ecto-1 rtkit-daemon[764977]: Failed to look up client: Device or resource busy
Sep 24 14:37:51 ecto-1 rtkit-daemon[764977]: Successfully made thread 789207 of process 789199 (/app/webkit/WebKitBuild/Debug/bin/WPEWebProcess) owned by '1000' RT at priority 5.
Sep 24 14:37:52 ecto-1 rtkit-daemon[764977]: Warning: Reached maximum concurrent process limit for user '1000', denying request.
Sep 24 14:37:52 ecto-1 rtkit-daemon[764977]: Failed to look up client: Device or resource busy
Sep 24 14:37:52 ecto-1 rtkit-daemon[764977]: Warning: Reached maximum concurrent process limit for user '1000', denying request.
Sep 24 14:37:52 ecto-1 rtkit-daemon[764977]: Failed to look up client: Device or resource busy
Sep 24 14:37:53 ecto-1 rtkit-daemon[764977]: Successfully made thread 789500 of process 789495 (/app/webkit/WebKitBuild/Debug/bin/WPEWebProcess) owned by '1000' RT at priority 5.
Sep 24 14:37:55 ecto-1 rtkit-daemon[764977]: Successfully made thread 789621 of process 789617 (/app/webkit/WebKitBuild/Debug/bin/WPEWebProcess) owned by '1000' RT at priority 5.
Sep 24 14:37:55 ecto-1 rtkit-daemon[764977]: Successfully made thread 789673 of process 789665 (/app/webkit/WebKitBuild/Debug/bin/WPEWebProcess) owned by '1000' RT at priority 5.
Sep 24 14:37:55 ecto-1 rtkit-daemon[764977]: Successfully made thread 789739 of process 789718 (/app/webkit/WebKitBuild/Debug/bin/WPEWebProcess) owned by '1000' RT at priority 5.
Sep 24 14:37:56 ecto-1 rtkit-daemon[764977]: Successfully made thread 789899 of process 789887 (/app/webkit/WebKitBuild/Debug/bin/WPEWebProcess) owned by '1000' RT at priority 5.
Sep 24 14:37:57 ecto-1 rtkit-daemon[764977]: Successfully made thread 789908 of process 789896 (/app/webkit/WebKitBuild/Debug/bin/WPEWebProcess) owned by '1000' RT at priority 5.
Sep 24 14:37:57 ecto-1 rtkit-daemon[764977]: Warning: Reached maximum concurrent process limit for user '1000', denying request.
Sep 24 14:37:57 ecto-1 rtkit-daemon[764977]: Failed to look up client: Device or resource busy
Sep 24 14:37:59 ecto-1 rtkit-daemon[764977]: Successfully made thread 790301 of process 790269 (/app/webkit/WebKitBuild/Debug/bin/WPEWebProcess) owned by '1000' RT at priority 5.
Sep 24 14:37:59 ecto-1 rtkit-daemon[764977]: Successfully made thread 790119 of process 790108 (/app/webkit/WebKitBuild/Debug/bin/WPEWebProcess) owned by '1000' RT at priority 5.
Sep 24 14:37:59 ecto-1 rtkit-daemon[764977]: Warning: Reached maximum concurrent process limit for user '1000', denying request.
Sep 24 14:37:59 ecto-1 rtkit-daemon[764977]: Failed to look up client: Device or resource busy
Sep 24 14:38:00 ecto-1 rtkit-daemon[764977]: Successfully made thread 790520 of process 790514 (/app/webkit/WebKitBuild/Debug/bin/WPEWebProcess) owned by '1000' RT at priority 5.
Sep 24 14:38:00 ecto-1 rtkit-daemon[764977]: Successfully made thread 790553 of process 790550 (/app/webkit/WebKitBuild/Debug/bin/WPEWebProcess) owned by '1000' RT at priority 5.
Sep 24 14:38:00 ecto-1 rtkit-daemon[764977]: Successfully made thread 790566 of process 790561 (/app/webkit/WebKitBuild/Debug/bin/WPEWebProcess) owned by '1000' RT at priority 5.
Sep 24 14:38:01 ecto-1 rtkit-daemon[764977]: Warning: Reached maximum concurrent process limit for user '1000', denying request.
Sep 24 14:38:01 ecto-1 rtkit-daemon[764977]: Failed to look up client: Device or resource busy
Sep 24 14:38:04 ecto-1 rtkit-daemon[764977]: Successfully made thread 790967 of process 790962 (/app/webkit/WebKitBuild/Debug/bin/WPEWebProcess) owned by '1000' RT at priority 5.
Sep 24 14:38:04 ecto-1 rtkit-daemon[764977]: Warning: Reached maximum concurrent process limit for user '1000', denying request.
Sep 24 14:38:04 ecto-1 rtkit-daemon[764977]: Failed to look up client: Device or resource busy
Sep 24 14:38:06 ecto-1 rtkit-daemon[764977]: Warning: Reached maximum concurrent process limit for user '1000', denying request.
Sep 24 14:38:06 ecto-1 rtkit-daemon[764977]: Failed to look up client: Device or resource busy
Sep 24 14:38:07 ecto-1 kernel: perf: interrupt took too long (4958 > 4951), lowering kernel.perf_event_max_sample_rate to 40000
Sep 24 14:38:07 ecto-1 rtkit-daemon[764977]: Successfully made thread 791308 of process 791291 (/app/webkit/WebKitBuild/Debug/bin/WPEWebProcess) owned by '1000' RT at priority 5.
Sep 24 14:38:08 ecto-1 rtkit-daemon[764977]: Warning: Reached maximum concurrent process limit for user '1000', denying request.
Sep 24 14:38:08 ecto-1 rtkit-daemon[764977]: Failed to look up client: Device or resource busy
Sep 24 14:38:10 ecto-1 rtkit-daemon[764977]: Successfully made thread 791555 of process 791545 (/app/webkit/WebKitBuild/Debug/bin/WPEWebProcess) owned by '1000' RT at priority 5.
Sep 24 14:38:11 ecto-1 rtkit-daemon[764977]: Warning: Reached maximum concurrent process limit for user '1000', denying request.
Sep 24 14:38:11 ecto-1 rtkit-daemon[764977]: Failed to look up client: Device or resource busy
Sep 24 14:38:14 ecto-1 rtkit-daemon[764977]: Successfully made thread 791896 of process 791892 (/app/webkit/WebKitBuild/Debug/bin/WPEWebProcess) owned by '1000' RT at priority 5.

Comment 1 Carlos Garcia Campos 2022-09-26 00:49:44 PDT

Demoting a thread from real time is not an operation that requires privileges and rtkit doesn't even have API to demote a particular thread. rtkit has some limits, so for example it has a default limit of 15 processes per user that can have real time threads, which is what you are reaching when running the tests. So, looking at the logs I'm not sure there's any issue there.

Comment 2 Philippe Normand 2022-09-26 01:25:30 PDT

Thanks. Closing this then!