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Fixes a 100% CPU usage on Konsole based terminal

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when Konsole terminal exited while nwipe is sitting at the
drive selection screen.

To avoid 100% CPU usage, check for a runaway condition caused by the
function "keystroke = getch() that immediately returns an error
condition. We check for an error condition because getch() returns a
ERR value when the timeout value "timeout( 250 );" expires as well as
when a real error occurs. We can't differentiate from normal operation
and a failure of the getch function to block for the specified period
of timeout. So here we check the while loop hasn't exceeded the number
of expected iterations per second ie. a timeout(250) block value of
250ms means we should not see any more than (1000/250) = 4 iterations.
We double this to 8 to allow a little tolerance. Why is this necessary?
It's been found that in KDE konsole and other terminals based on the QT
terminal engine exiting the terminal without first existing nwipe
results in nwipe remaining running but detached from any interface
which causes getch to fail and its associated timeout. So the CPU or
CPU core rises to 100%. Here we detect that failure and exit nwipe
gracefully with the appropriate error. This does not affect use of
tmux for attaching or detaching from a running nwipe session when
sitting at the selection screen. All other terminals correctly
terminate nwipe when the terminal itself is exited.
This commit is contained in:
PartialVolume
2022-03-02 19:28:55 +00:00
parent 58576f8191
commit 175b246291
3 changed files with 67 additions and 10 deletions
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71
src/gui.c
View File

@@ -639,6 +639,18 @@ void nwipe_gui_select( int count, nwipe_context_t** c )
time_t temperature_check_time = time( NULL );
/* Used in the selection loop to trap a failure of the timeout(), getch() mechanism to block for the designated
* period */
int iteration_counter;
/* Used in the selection loop to trap a failure of the timeout(), getch() mechanism to block for the designated
* period */
int expected_iterations;
time_t iteration_timestamp;
time_t previous_iteration_timestamp;
do
{
@@ -847,21 +859,64 @@ void nwipe_gui_select( int count, nwipe_context_t** c )
/* Output to physical screen */
doupdate();
/* Wait 250ms for input from getch, if nothing getch will then continue,
* This is necessary so that the while loop can be exited by the
* terminate_signal e.g.. the user pressing control-c to exit.
* Do not change this value, a higher value means the keys become
* sluggish, any slower and more time is spent unnecessarily looping
* which wastes CPU cycles.
*/
/* Initialise the iteration counter */
iteration_counter = 0;
previous_iteration_timestamp = time( NULL );
/* Calculate Maximum allowed iterations per second */
expected_iterations = ( 1000 / GETCH_BLOCK_MS ) * 2;
do
{
/* Wait 250ms for input from getch, if nothing getch will then continue,
* This is necessary so that the while loop can be exited by the
* terminate_signal e.g.. the user pressing control-c to exit.
* Do not change this value, a higher value means the keys become
* sluggish, any slower and more time is spent unnecessarily looping
* which wastes CPU cycles.
*/
validkeyhit = 0;
timeout( 250 ); // block getch() for 250ms.
timeout( GETCH_BLOCK_MS ); // block getch() for ideally about 250ms.
keystroke = getch(); // Get user input.
timeout( -1 ); // Switch back to blocking mode.
/* To avoid 100% CPU usage, check for a runaway condition caused by the "keystroke = getch(); (above), from
* immediately returning an error condition. We check for an error condition because getch() returns a ERR
* value when the timeout value "timeout( 250 );" expires as well as when a real error occurs. We can't
* differentiate from normal operation and a failure of the getch function to block for the specified period
* of timeout. So here we check the while loop hasn't exceeded the number of expected iterations per second
* ie. a timeout(250) block value of 250ms means we should not see any more than (1000/250) = 4 iterations.
* We double this to 8 to allow a little tolerance. Why is this necessary? It's been found that in KDE
* konsole and other terminals based on the QT terminal engine exiting the terminal without first existing
* nwipe results in nwipe remaining running but detached from any interface which causes getch to fail and
* its associated timeout. So the CPU or CPU core rises to 100%. Here we detect that failure and exit nwipe
* gracefully with the appropriate error. This does not affect use of tmux for attaching or detaching from a
* running nwipe session when sitting at the selection screen. All other terminals correctly terminate nwipe
* when the terminal itself is exited.
*/
iteration_counter++;
if( previous_iteration_timestamp == time( NULL ) )
{
if( iteration_counter > expected_iterations )
{
nwipe_log( NWIPE_LOG_ERROR,
"GUI.c,nwipe_gui_select(), loop runaway, did you close the terminal without exiting "
"nwipe? Initiating shutdown now." );
/* Issue signal to nwipe to shutdown immediately but gracefully */
terminate_signal = 1;
}
}
else
{
/* new second, so reset counter */
iteration_counter = 0;
previous_iteration_timestamp = time( NULL );
}
/* We don't necessarily use all of these. For future reference these are some CTRL+key values
* ^A - 1, ^B - 2, ^D - 4, ^E - 5, ^F - 6, ^G - 7, ^H - 8, ^I - 9, ^K - 11, ^L - 12, ^N - 14,
* ^O - 15, ^P - 16, ^R - 18, ^T - 20, ^U - 21, ^V - 22, ^W - 23, ^X - 24, ^Y - 25

2
src/gui.h
View File

@@ -50,4 +50,6 @@ void nwipe_update_speedring( nwipe_speedring_t* speedring, u64 speedring_done, t
#define NOMENCLATURE_RESULT_STR_SIZE 8
#define GETCH_BLOCK_MS 250 /* millisecond block time for getch() */
#endif /* GUI_H_ */

4
src/version.c
View File

@@ -4,7 +4,7 @@
* used by configure to dynamically assign those values
* to documentation files.
*/
const char* version_string = "0.32.025";
const char* version_string = "0.32.026";
const char* program_name = "nwipe";
const char* author_name = "Martijn van Brummelen";
const char* email_address = "git@brumit.nl";
@@ -14,4 +14,4 @@ Modifications to original dwipe Copyright Andy Beverley <andy@andybev.com>\n\
This is free software; see the source for copying conditions.\n\
There is NO warranty; not even for MERCHANTABILITY or FITNESS\n\
FOR A PARTICULAR PURPOSE.\n";
const char* banner = "nwipe 0.32.025";
const char* banner = "nwipe 0.32.026";