Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
x86/tsc: Handle CLOCK_SOURCE_VALID_FOR_HRES correctly
Unconditionally setting the CLOCK_SOURCE_VALID_FOR_HRES for the real TSC
clocksource is wrong as there is no guarantee that the early TSC was
validated for high resolution mode.
Set the flag only when the early TSC was validated as otherwise the
clocksource selection might enable high resolution mode with a TSC of
unknown quality and possibly no way to back out once it is discovered to be
unsuitable.
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260123231521.790598171@kernel.org
+9
-1
+9
-1
arch/x86/kernel/tsc.c
+9
-1
arch/x86/kernel/tsc.c
···
1200
1200
.read = read_tsc,
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1201
.mask = CLOCKSOURCE_MASK(64),
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.flags = CLOCK_SOURCE_IS_CONTINUOUS |
1203
-
CLOCK_SOURCE_VALID_FOR_HRES |
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1203
CLOCK_SOURCE_CAN_INLINE_READ |
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1204
CLOCK_SOURCE_MUST_VERIFY |
1206
1205
CLOCK_SOURCE_VERIFY_PERCPU |
···
1410
1411
have_art = true;
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1412
clocksource_tsc.base = &art_base_clk;
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1413
}
1414
+
1415
+
/*
1416
+
* Transfer the valid for high resolution flag if it was set on the
1417
+
* early TSC already. That guarantees that there is no intermediate
1418
+
* clocksource selected once the early TSC is unregistered.
1419
+
*/
1420
+
if (clocksource_tsc_early.flags & CLOCK_SOURCE_VALID_FOR_HRES)
1421
+
clocksource_tsc.flags |= CLOCK_SOURCE_VALID_FOR_HRES;
1422
+
1413
1423
clocksource_register_khz(&clocksource_tsc, tsc_khz);
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unreg:
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1425
clocksource_unregister(&clocksource_tsc_early);