Boot time labs: use "usleep 1000" instead of "sleep 0.001"

Better to recommend "usleep" than "sleep" here Signed-off-by: Michael Opdenacker <michael.opdenacker@bootlin.com>
bootlin · Oct 22, 2021 · 3016929 · 3016929
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Showing 4 changed files with 5 additions and 6 deletions.
diff --git a/lab-data/boot-time/rootfs/data/playvideo b/lab-data/boot-time/rootfs/data/playvideo
@@ -4,7 +4,7 @@ then
    echo "Waiting for /dev/video0 to be ready..."
    while ! [ -e /dev/video0 ]
    do
-       sleep 0.001
+       usleep 1000
    done
 fi
 echo "Starting ffmpeg"

diff --git a/labs/boot-time-application/boot-time-application.tex b/labs/boot-time-application/boot-time-application.tex
@@ -246,7 +246,7 @@ \section{Putting things back together}
    echo "Waiting for /dev/video0 to be ready..."
    while ! [ -e /dev/video0 ]
    do
-       sleep 0.001
+       usleep 1000
    done
 fi
 \end{verbatim}
@@ -256,8 +256,6 @@ \section{Putting things back together}
 \item It seems you can not run an empty \code{while} loop with BusyBox
       \code{sh}. That's why I had to put a real command (not a comment)
       inside the loop.
-\item Fortunately, the \code{sleep} command supports subsecond waiting.
-      Did you know?
 \item When we optimize the kernel, we will try to address this camera
       readiness issue. If we can't fix it, at least we will display
       something on the screen to make the user wait.

diff --git a/labs/boot-time-filesystem-optimizations/boot-time-filesystem-optimizations.tex b/labs/boot-time-filesystem-optimizations/boot-time-filesystem-optimizations.tex
@@ -149,7 +149,7 @@ \section{Initramfs tests}
    echo "Waiting for /dev/video0 to be ready..." > /dev/console
    while ! [ -e /dev/video0 ]
    do
-       sleep 0.001
+       usleep 1000
    done
 fi
 echo "Starting ffmpeg" > /dev/console

diff --git a/labs/boot-time-init-scripts/boot-time-init-scripts.tex b/labs/boot-time-init-scripts/boot-time-init-scripts.tex
@@ -346,7 +346,8 @@ \subsection{Reducing BusyBox to the minimum}
   \end{itemize}
   \item In \code{Coreutils}:
   \begin{itemize}
-     \item Support for the \code{sleep} command, with support for fractional arguments.
+     \item Support for the \code{usleep} command, allowing to specify
+           sleep time in microseconds.
      \item Support for the \code{echo} command, without additional options.
      \item Enable \code{test} and \code{test as [}
      \item Disable \code{Extend test to 64 bit}