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perf test waiting.sh: Replace timestamp polling with sleep

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The waiting helpers implement timeouts using:

  date +%s%1N

This relies on GNU coreutils date truncating %N to the specified width,
so %1N yields tenths of a second.

Rust coreutils (uutils) interprets the width differently and does not
truncate the nanoseconds field.  Consequently "date +%1N" returns all
nine nanosecond digits, causing the elapsed-time calculation to be done
in nanoseconds while timeout values remain in tenths of a second.

As a result, timeout comparisons succeed immediately and the waiting
helpers time out on their first iteration.  This causes
test_intel_pt.sh to fail on systems using uutils "date".

Avoid implementation-specific date formatting entirely.  Instead, wait
for 100 ms on each iteration and count the timeout down.  Besides fixing
the portability issue, this removes the busy-waiting behaviour in
wait_for_perf_to_start(), which could otherwise consume CPU while
waiting for perf record to start.

Since the timeout is now based on repeated sleeps, it is only
approximate.  Update the comments accordingly.  Also make is_running()
wait for exactly the documented number of tenths by changing its timeout
test from -gt to the new logic, and quote tm_out in the modified code.

Reviewed-by: Ian Rogers <irogers@google.com>
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Adrian Hunter 2026-09-08 18:20:53 +03:00 committed by Arnaldo Carvalho de Melo
parent 87923c8f4a
commit ee32ee73cc
1 changed files with 16 additions and 18 deletions
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34
tools/perf/tests/shell/lib/waiting.sh
View File

@ -1,77 +1,75 @@
#!/bin/bash
# SPDX-License-Identifier: GPL-2.0
tenths=date\ +%s%1N
# Wait for PID $1 to have $2 number of threads started
# Time out after $3 tenths of a second or 5 seconds if $3 is ""
# Time out after approx. $3 tenths of a second or 5 seconds if $3 is ""
wait_for_threads()
{
tm_out=$3 ; [ -n "${tm_out}" ] || tm_out=50
start_time=$($tenths)
while [ -e "/proc/$1/task" ] ; do
th_cnt=$(find "/proc/$1/task" -mindepth 1 -maxdepth 1 -printf x | wc -c)
if [ "${th_cnt}" -ge "$2" ] ; then
return 0
fi
# Wait at most tm_out tenths of a second
if [ $(($($tenths) - start_time)) -ge $tm_out ] ; then
if [ "${tm_out}" -le 0 ] ; then
echo "PID $1 does not have $2 threads"
return 1
fi
sleep 0.1
tm_out=$((tm_out - 1))
done
return 1
}
# Wait for perf record -vvv 2>$2 with PID $1 to start by looking at file $2
# It depends on capturing perf record debug message "perf record has started"
# Time out after $3 tenths of a second or 5 seconds if $3 is ""
# Time out after approx. $3 tenths of a second or 5 seconds if $3 is ""
wait_for_perf_to_start()
{
tm_out=$3 ; [ -n "${tm_out}" ] || tm_out=50
echo "Waiting for \"perf record has started\" message"
start_time=$($tenths)
while [ -e "/proc/$1" ] ; do
if grep -q "perf record has started" "$2" ; then
echo OK
break
fi
# Wait at most tm_out tenths of a second
if [ $(($($tenths) - start_time)) -ge $tm_out ] ; then
if [ "${tm_out}" -le 0 ] ; then
echo "perf recording did not start"
return 1
fi
sleep 0.1
tm_out=$((tm_out - 1))
done
return 0
}
# Wait for process PID %1 to exit
# Time out after $2 tenths of a second or 5 seconds if $2 is ""
# Time out after approx. $2 tenths of a second or 5 seconds if $2 is ""
wait_for_process_to_exit()
{
tm_out=$2 ; [ -n "${tm_out}" ] || tm_out=50
start_time=$($tenths)
while [ -e "/proc/$1" ] ; do
# Wait at most tm_out tenths of a second
if [ $(($($tenths) - start_time)) -ge $tm_out ] ; then
if [ "${tm_out}" -le 0 ] ; then
echo "PID $1 did not exit as expected"
return 1
fi
sleep 0.1
tm_out=$((tm_out - 1))
done
return 0
}
# Check if PID $1 is still running after $2 tenths of a second
# Check if PID $1 is still running after approx. $2 tenths of a second
# or 0.3 seconds if $2 is ""
is_running()
{
tm_out=$2 ; [ -n "${tm_out}" ] || tm_out=3
start_time=$($tenths)
while [ -e "/proc/$1" ] ; do
# Check for at least tm_out tenths of a second
if [ $(($($tenths) - start_time)) -gt $tm_out ] ; then
if [ "${tm_out}" -le 0 ] ; then
return 0
fi
sleep 0.1
tm_out=$((tm_out - 1))
done
echo "PID $1 exited prematurely"
return 1