When debug preempt or preempt tracer is enabled, preempt_count_add/sub()
can be traced by function and function graph tracing, and
preempt_disable/enable() would call preempt_count_add/sub(), so in Ftrace
subsystem we should use preempt_disable/enable_notrace instead.
In the commit 345ddcc882 ("ftrace: Have set_ftrace_pid use the bitmap
like events do") the function this_cpu_read() was added to
trace_graph_entry(), and if this_cpu_read() calls preempt_disable(), graph
tracer will go into a recursive loop, even if the tracing_on is
disabled.
So this patch change to use preempt_enable/disable_notrace instead in
this_cpu_read().
Since Yonghui Yang helped a lot to find the root cause of this problem,
so also add his SOB.
Signed-off-by: Yonghui Yang <mark.yang@spreadtrum.com>
Signed-off-by: Chunyan Zhang <zhang.chunyan@linaro.org>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Nobody seems to be producing !SMP systems anymore, so this is just
becoming a source of kernel bugs, particularly if people want to use
coherent DMA with non-shared pages.
This patch forces CONFIG_SMP=y for arm64, removing a modest amount of
code in the process.
Signed-off-by: Will Deacon <will.deacon@arm.com>
this_cpu operations were implemented for arm64 in:
5284e1b arm64: xchg: Implement cmpxchg_double
f97fc81 arm64: percpu: Implement this_cpu operations
Unfortunately, it is possible for pre-emption to take place between
address generation and data access. This can lead to cases where data
is being manipulated by this_cpu for a different CPU than it was
called on. Which effectively breaks the spec.
This patch disables pre-emption for the this_cpu operations
guaranteeing that address generation and data manipulation take place
without a pre-emption in-between.
Fixes: 5284e1b4bc ("arm64: xchg: Implement cmpxchg_double")
Fixes: f97fc81079 ("arm64: percpu: Implement this_cpu operations")
Reported-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Steve Capper <steve.capper@linaro.org>
[catalin.marinas@arm.com: remove space after type cast]
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
The generic this_cpu operations disable interrupts to ensure that the
requested operation is protected from pre-emption. For arm64, this is
overkill and can hurt throughput and latency.
This patch provides arm64 specific implementations for the this_cpu
operations. Rather than disable interrupts, we use the exclusive
monitor or atomic operations as appropriate.
The following operations are implemented: add, add_return, and, or,
read, write, xchg. We also wire up a cmpxchg implementation from
cmpxchg.h.
Testing was performed using the percpu_test module and hackbench on a
Juno board running 3.18-rc4.
Signed-off-by: Steve Capper <steve.capper@linaro.org>
Reviewed-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
To support both Clang and GCC, use the global stack register variable vs
a local register variable.
Author: Mark Charlebois <charlebm@gmail.com>
Signed-off-by: Mark Charlebois <charlebm@gmail.com>
Signed-off-by: Behan Webster <behanw@converseincode.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Commit fb4a96029c (arm64: kernel: fix per-cpu offset restore on
resume) uses per_cpu_offset() unconditionally during CPU wakeup,
however, this is only defined for the SMP case.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Reported-by: Dave P Martin <Dave.Martin@arm.com>
This patch implements optimised percpu variable accesses using the
el1 r/w thread register (tpidr_el1) along the same lines as arch/arm/.
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
