bamfdaemon polling every 3 ms

Bug #1710751 reported by jimav on 2017-08-15
6
This bug affects 1 person
Affects Status Importance Assigned to Milestone
bamf (Ubuntu)
Undecided
Unassigned

Bug Description

bamfdaemon has some odd behavior (possibly indicating a design bug) which causes it to wake up every 3 milliseconds and attempt four non-blocking reads on the same socket. This occurs in an otherwise idle system.

Most likely the code uses a short-cut or work-around for a design problem somewhere.

Ideally bamfdaemon would call poll() or select() and block _indefinitely_ (no timeout) until an event of possible interest occurs, and only then attempt the recvmsg() calls. That would avoid loading the cpu and forcing the bamf memory pages to stay resident, etc.

Can someone who knows what bamfdaemon is trying to do comment on why it is waking up every 3 ms. to repeat the exact same recvmsg() calls?

Strangely, it seems to call recvmsg() several times on the same file descriptor, with a different buffer address each time (no kernel calls inbetween).

STEPS TO REPRODUCE:

sudo strace -p `pidof bamfdaemon`

RESULTS:

recvmsg(3, {msg_name(0)=NULL, msg_iov(1)=[{"\34\0\0\375\20\0\200\3\253\1\0\0\263\214[\26\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", 4096}], msg_controllen=0, msg_flags=0}, 0) = 32
recvmsg(3, 0x7ffe096ef630, 0) = -1 EAGAIN (Resource temporarily unavailable)
recvmsg(3, 0x7ffe096ef4e0, 0) = -1 EAGAIN (Resource temporarily unavailable)
recvmsg(3, 0x7ffe096ef610, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=3, events=POLLIN}, {fd=4, events=POLLIN}, {fd=5, events=POLLIN}], 3, -1) = 1 ([{fd=3, revents=POLLIN}])

(repeats forever)

ProblemType: Bug
DistroRelease: Ubuntu 17.04
Package: bamfdaemon 0.5.3+17.04.20170406-0ubuntu1
ProcVersionSignature: Ubuntu 4.10.0-30.34-generic 4.10.17
Uname: Linux 4.10.0-30-generic x86_64
NonfreeKernelModules: nvidia_uvm nvidia_drm nvidia_modeset nvidia
ApportVersion: 2.20.4-0ubuntu4.5
Architecture: amd64
CurrentDesktop: Unity:Unity7
Date: Mon Aug 14 18:09:28 2017
InstallationDate: Installed on 2017-01-19 (207 days ago)
InstallationMedia: Ubuntu 16.04.1 LTS "Xenial Xerus" - Release amd64 (20160719)
SourcePackage: bamf
UpgradeStatus: Upgraded to zesty on 2017-07-26 (19 days ago)

jimav (james-avera) wrote :
jimav (james-avera) wrote :

Oh never mind. Some process is sending it a continuous stream of messages, so of course it is waking up all the time...

Changed in bamf (Ubuntu):
status: New → Invalid
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