c8849dd8d5
The previous implementation required one syscall per child we're waiting on to see which one exited. That means the algorithm was O(n). This implementation uses WNOWAIT to find out which child exited and then goes straight to that one. So it's O(1) on the number of children, but runs 2 * number_of_children_that_exited + 1 syscalls, assuming there are no race conditions with other threads. If there are or if a child not started by forkfd exits, we'll still iterate over each child we're managing to see which one exited. It modifies the existing code so that it will do a waitid() with WNOWAIT to check on the status of the child: if the child has exited, we'll try to lock the entry so only one thread will do the final wait(). In the case we read the PID, then the child exited, was reaped by another thread, the PID got recycled and that child exited again, we'll fail to lock the ProcessInfo entry so no harm comes. If by an absurd coincidence this other child was started by forkfd() and its ProcessInfo is exactly the one we are looking at, then we'll succeed in locking but that's a benign race: we'll do what the other thread was trying to do and the other thread will give up. Future improvements to the algorithm are discussed in the Gerrit change. Change-Id: Ie74836dbc388cd9b3fa375a41a8d944602a32df1 Reviewed-by: Thiago Macieira <thiago.macieira@intel.com> |
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| .. | ||
| auto | ||
| baselineserver | ||
| benchmarks | ||
| global | ||
| manual | ||
| shared | ||
| README | ||
| tests.pro | ||
This directory contains autotests and benchmarks based on Qt Test. In order
to run the autotests reliably, you need to configure a desktop to match the
test environment that these tests are written for.
Linux X11:
* The user must be logged in to an active desktop; you can't run the
autotests without a valid DISPLAY that allows X11 connections.
* The tests are run against a KDE3 or KDE4 desktop.
* Window manager uses "click to focus", and not "focus follows mouse". Many
tests move the mouse cursor around and expect this to not affect focus
and activation.
* Disable "click to activate", i.e., when a window is opened, the window
manager should automatically activate it (give it input focus) and not
wait for the user to click the window.