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mirror of https://github.com/edk2-porting/linux-next.git synced 2024-12-25 13:43:55 +08:00
linux-next/kernel/debug
Daniel Thompson d04213af90 kdb: Simplify code to fetch characters from console
Currently kdb_read_get_key() contains complex control flow that, on
close inspection, turns out to be unnecessary. In particular:

1. It is impossible to enter the branch conditioned on (escape_delay == 1)
   except when the loop enters with (escape_delay == 2) allowing us to
   combine the branches.

2. Most of the code conditioned on (escape_delay == 2) simply modifies
   local data and then breaks out of the loop causing the function to
   return escape_data[0].

3. Based on #2 there is not actually any need to ever explicitly set
   escape_delay to 2 because we it is much simpler to directly return
   escape_data[0] instead.

4. escape_data[0] is, for all but one exit path, known to be '\e'.

Simplify the code based on these observations.

There is a subtle (and harmless) change of behaviour resulting from this
simplification: instead of letting the escape timeout after ~1998
milliseconds we now timeout after ~2000 milliseconds

Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20191025073328.643-3-daniel.thompson@linaro.org
2019-10-28 12:02:21 +00:00
..
kdb kdb: Simplify code to fetch characters from console 2019-10-28 12:02:21 +00:00
debug_core.c kdb: Avoid array subscript warnings on non-SMP builds 2019-10-24 15:34:58 +01:00
debug_core.h kdb: Fix stack crawling on 'running' CPUs that aren't the master 2019-10-10 16:28:48 +01:00
gdbstub.c gdbstub: Replace strcpy() by strscpy() 2019-05-02 13:40:27 +01:00
Makefile treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00