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xz: Improve the comment about start_time in mytime.c.

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start_time is relative to an arbitary point in time, it's not
time of day, so using it for anything else than time differences
wouldn't make sense.
This commit is contained in:
Lasse Collin 2023-02-07 19:07:45 +02:00
parent 7673ef5aa8
commit 1dbe12b90c
1 changed files with 10 additions and 5 deletions
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15
src/xz/mytime.c
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@ -20,11 +20,16 @@
uint64_t opt_flush_timeout = 0; uint64_t opt_flush_timeout = 0;
// The start_time variable will not represent the actual start time // start_time holds the time when the (de)compression was started.
// if mytime_sigtstp_handler() executes. The signal handler measures // It's from mytime_now() and thus only useful for calculating relative
// the amount of time spent stopped and adds it to start_time. // time differences (elapsed time). start_time is initialized by calling
// So, care must be taken in the future if the actual start time needs // mytime_set_start_time() and modified by mytime_sigtstp_handler().
// to be displayed for any reason. //
// When mytime_sigtstp_handler() is used, start_time is made volatile.
// I'm not sure if that is really required since access to it is guarded
// by signals_block()/signals_unblock() since accessing an uint64_t isn't
// atomic on all systems. But since the variable isn't accessed very
// frequently making it volatile doesn't hurt.
#ifdef USE_SIGTSTP_HANDLER #ifdef USE_SIGTSTP_HANDLER
static volatile uint64_t start_time; static volatile uint64_t start_time;
#else #else