git: 108de784513d - main - Redefine CLOCK_BOOTTIME to alias CLOCK_MONOTONIC, not CLOCK_UPTIME

The branch main has been updated by imp:

URL: https://cgit.FreeBSD.org/src/commit/?id=108de784513d87bbe850e7b003a73e26b5b54caa

commit 108de784513d87bbe850e7b003a73e26b5b54caa
Author:     Val Packett <val@packett.cool>
AuthorDate: 2024-05-31 14:45:02 +0000
Commit:     Warner Losh <imp@FreeBSD.org>
CommitDate: 2024-05-31 14:45:02 +0000

    Redefine CLOCK_BOOTTIME to alias CLOCK_MONOTONIC, not CLOCK_UPTIME
    
    The suspend-awareness situation with monotonic clocks across platforms
    is kind of a mess, let's try not making it worse.
    
    On Linux, CLOCK_MONOTONIC does NOT count suspended time, and
    CLOCK_BOOTTIME was introduced to INCLUDE suspended time.
    
    On OpenBSD, CLOCK_MONOTONIC DOES count suspended time, and CLOCK_UPTIME
    was introduced to EXCLUDE suspended time.
    
    On macOS, it's the same as OpenBSD, but with CLOCK_UPTIME_RAW.
    
    Right now, we do not have a monotonic clock that counts suspended time.
    We have CLOCK_UPTIME as a distinct ID alias, and CLOCK_BOOTTIME as a
    preprocessor alias, both being effectively `CLOCK_MONOTONIC` for now.
    
    When we introduce a suspend-aware clock in the future, it would make a
    lot more sense to do it the OpenBSD/macOS way, i.e. to make
    CLOCK_MONOTONIC include suspended time and make CLOCK_UPTIME exclude it,
    because that's what the name CLOCK_UPTIME implies: a deviation from the
    default intended for the uptime command to allow it to only show the
    time the system was actually up and not suspended.
    
    Let's change the define right now to make sure software using the define
    would not end up using the ID of the wrong clock in the future, and fix
    the IDs in the Linux compat code to match the expected changes too.
    
    See https://bugzilla.mozilla.org/show_bug.cgi?id=1824084
    for more discussion.
    
    Fixes:          155f15118a77 ("clock_gettime: Add Linux aliases for CLOCK_*")
    Fixes:          25ada637362d ("Map Linux CLOCK_BOOTTIME to native CLOCK_UPTIME.")
    Sponsored by:   https://www.patreon.com/valpackett
    Reviewed by:    kib, imp
    Differential Revision:  https://reviews.freebsd.org/D39270
---
 sys/compat/linux/linux_time.c | 6 +++---
 sys/sys/_clock_id.h           | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/sys/compat/linux/linux_time.c b/sys/compat/linux/linux_time.c
index e9e5cf075210..f4dd26dd3d2a 100644
--- a/sys/compat/linux/linux_time.c
+++ b/sys/compat/linux/linux_time.c
@@ -287,7 +287,7 @@ linux_to_native_clockid(clockid_t *n, clockid_t l)
 		*n = CLOCK_REALTIME;
 		break;
 	case LINUX_CLOCK_MONOTONIC:
-		*n = CLOCK_MONOTONIC;
+		*n = CLOCK_UPTIME;
 		break;
 	case LINUX_CLOCK_PROCESS_CPUTIME_ID:
 		*n = CLOCK_PROCESS_CPUTIME_ID;
@@ -300,10 +300,10 @@ linux_to_native_clockid(clockid_t *n, clockid_t l)
 		break;
 	case LINUX_CLOCK_MONOTONIC_COARSE:
 	case LINUX_CLOCK_MONOTONIC_RAW:
-		*n = CLOCK_MONOTONIC_FAST;
+		*n = CLOCK_UPTIME_FAST;
 		break;
 	case LINUX_CLOCK_BOOTTIME:
-		*n = CLOCK_UPTIME;
+		*n = CLOCK_MONOTONIC;
 		break;
 	case LINUX_CLOCK_REALTIME_ALARM:
 	case LINUX_CLOCK_BOOTTIME_ALARM:
diff --git a/sys/sys/_clock_id.h b/sys/sys/_clock_id.h
index 47a551428dc3..728346a0f0ab 100644
--- a/sys/sys/_clock_id.h
+++ b/sys/sys/_clock_id.h
@@ -78,7 +78,7 @@
  * Linux compatible names.
  */
 #if __BSD_VISIBLE
-#define	CLOCK_BOOTTIME		CLOCK_UPTIME
+#define	CLOCK_BOOTTIME		CLOCK_MONOTONIC
 #define	CLOCK_REALTIME_COARSE	CLOCK_REALTIME_FAST
 #define	CLOCK_MONOTONIC_COARSE	CLOCK_MONOTONIC_FAST
 #endif