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Kernel: Ensure we don't get in an endless loop while querying the CMOS

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When we try to query the time from the RTC CMOS, we try to check if
the CMOS is updated. If it is updated for a long period of time (as a
result of hardware malfunction), break the loop and return Unix epoch
time.
This commit is contained in:
Liav A 2021-07-23 20:16:24 +03:00 committed by Andreas Kling
parent 74c9587798
commit 517460d3a9
Notes: sideshowbarker 2024-07-18 07:29:22 +09:00 
Author: https://github.com/supercomputer7
Commit: https://github.com/SerenityOS/serenity/commit/517460d3a9d
Pull-request: https://github.com/SerenityOS/serenity/pull/8964
Reviewed-by: https://github.com/awesomekling
Reviewed-by: https://github.com/caoimhebyrne
1 changed files with 22 additions and 2 deletions
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24
Kernel/RTC.cpp
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@ -6,6 +6,7 @@
#include <AK/Time.h>
#include <Kernel/CMOS.h>
#include <Kernel/IO.h>
#include <Kernel/RTC.h>
namespace RTC {
@ -34,8 +35,27 @@ static u8 bcd_to_binary(u8 bcd)
void read_registers(unsigned& year, unsigned& month, unsigned& day, unsigned& hour, unsigned& minute, unsigned& second)
{
while (update_in_progress())
;
// Note: Let's wait 0.01 seconds until we stop trying to query the RTC CMOS
size_t time_passed_in_milliseconds = 0;
bool update_in_progress_ended_successfully = false;
while (time_passed_in_milliseconds < 100) {
if (!update_in_progress()) {
update_in_progress_ended_successfully = true;
break;
}
IO::delay(1000);
time_passed_in_milliseconds++;
}
if (!update_in_progress_ended_successfully) {
year = 1970;
month = 1;
day = 1;
hour = 0;
minute = 0;
second = 0;
return;
}
u8 status_b = CMOS::read(0x0b);