[screen-devel] [bug #57697] 4.99.0: CPU usage always 100% after the commit 8becc4d (Convert select() to poll() in sched.c)

[Koichi Murase]

URL:
  <https://savannah.gnu.org/bugs/?57697>

                 Summary: 4.99.0: CPU usage always 100% after the commit
8becc4d (Convert select() to poll() in sched.c)
                 Project: GNU Screen
            Submitted by: akinomyoga
            Submitted on: Thu 30 Jan 2020 02:46:45 AM UTC
                Category: Crash/Freeze/Infloop
                Severity: 3 - Normal
                Priority: 5 - Normal
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 4.99.0
           Fixed Release: None
         Planned Release: None
           Work Required: None

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Details:

Hello, I'm trying the master branch (screen-4.99.0) for 24-bit color
support, but I noticed that the CPU usage of the main screen process
is always 100%.  I confirmed this with two Linux hosts:

  $ uname -a
  Linux song123 5.3.0-26-generic #28~18.04.1-Ubuntu SMP Wed Dec 18 16:40:14
UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
  $ uname -a
  Linux chatoyancy 5.1.20-300.fc30.x86_64 #1 SMP Fri Jul 26 15:03:11 UTC 2019
x86_64 x86_64 x86_64 GNU/Linux

I checked recent commits in the git repository and found that this
started to happen after the following commit:

  --------------------------------------------------------------------
  commit 8becc4d29a12688b39312639f56e1aeeb76f96e2 (HEAD)
  Author: Amadeusz Sławiński <address@hidden>
  Date:   Sun Nov 3 00:31:59 2019 +0100

      Convert select() to poll() in sched.c

      select() limits number of file descriptors that can be used by screen.
      Migrate to poll() to avoid this limitation.

      As can be seen in case of scheduler it requires quite some changes,
care
      must be taken to count poll() events properly.

      Bug: 55697

      Signed-off-by: Amadeusz Sławiński <address@hidden>
  --------------------------------------------------------------------




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