ARM: hw_breakpoint: do not allocate new breakpoints with preemption disabled

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The watchpoint single-stepping code calls register_user_hw_breakpoint to
register a mismatch breakpoint for stepping over the watchpoint. This is
performed with preemption disabled, which is unsafe as we may end up scheduling
whilst in_atomic(). Furthermore, using the perf API is rather overkill since
we are already in the hw-breakpoint backend and only require access to reserved
breakpoints anyway.

This patch reworks the watchpoint stepping code so that we don't require
another perf_event for the mismatch breakpoint. Instead, we hold a separate
arch_hw_breakpoint_ctrl struct inside the watchpoint which is used exclusively
for stepping. We can check whether or not stepping is enabled when installing
or uninstalling the watchpoint and operate on the breakpoint accordingly.

Signed-off-by: Will Deacon <will.deacon@arm.com>

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This commit is contained in:

Will Deacon 2010-11-29 16:56:01 +00:00

parent 0017ff42ac

commit 93a04a3416

2 changed files with 78 additions and 58 deletions

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2

arch/arm/include/asm/hw_breakpoint.h

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134

arch/arm/kernel/hw_breakpoint.c

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