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| author | Will Deacon <will.deacon@arm.com> | 2012-07-06 15:43:03 +0100 |
|---|---|---|
| committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2012-07-09 17:41:10 +0100 |
| commit | 575320d625d5b5eb115575a1f5e17af456e69577 (patch) | |
| tree | dc44829a23c7eb3d6da82533853a3c9d304df6d7 /arch/arm/Kconfig.debug | |
| parent | 27a5569dc66ecce06cb532542ddcd0b6da8783f6 (diff) | |
| download | lwn-575320d625d5b5eb115575a1f5e17af456e69577.tar.gz lwn-575320d625d5b5eb115575a1f5e17af456e69577.zip | |
ARM: 7445/1: mm: update CONTEXTIDR register to contain PID of current process
This patch introduces a new Kconfig option which, when enabled, causes
the kernel to write the PID of the current task into the PROCID field
of the CONTEXTIDR on context switch. This is useful when analysing
hardware trace, since writes to this register can be configured to emit
an event into the trace stream.
The thread notifier for writing the PID is deliberately kept separate
from the ASID-writing code so that we can support newer processors using
LPAE, where the ASID is stored in TTBR0. As such, the switch_mm code is
updated to perform a read-modify-write sequence to ensure that we don't
clobber the PID on CPUs using the classic 2-level page tables.
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm/Kconfig.debug')
| -rw-r--r-- | arch/arm/Kconfig.debug | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug index 01a134141216..521e15bc6401 100644 --- a/arch/arm/Kconfig.debug +++ b/arch/arm/Kconfig.debug @@ -369,4 +369,13 @@ config ARM_KPROBES_TEST help Perform tests of kprobes API and instruction set simulation. +config PID_IN_CONTEXTIDR + bool "Write the current PID to the CONTEXTIDR register" + depends on CPU_COPY_V6 + help + Enabling this option causes the kernel to write the current PID to + the PROCID field of the CONTEXTIDR register, at the expense of some + additional instructions during context switch. Say Y here only if you + are planning to use hardware trace tools with this kernel. + endmenu |