• Frederic Weisbecker's avatar
    hw-breakpoints: Modify breakpoints without unregistering them · 44234adc
    Frederic Weisbecker authored
    Currently, when ptrace needs to modify a breakpoint, like disabling
    it, changing its address, type or len, it calls
    modify_user_hw_breakpoint(). This latter will perform the heavy and
    racy task of unregistering the old breakpoint and registering a new
    one.
    
    This is racy as someone else might steal the reserved breakpoint
    slot under us, which is undesired as the breakpoint is only
    supposed to be modified, sometimes in the middle of a debugging
    workflow. We don't want our slot to be stolen in the middle.
    
    So instead of unregistering/registering the breakpoint, just
    disable it while we modify its breakpoint fields and re-enable it
    after if necessary.
    Signed-off-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Prasad <prasad@linux.vnet.ibm.com>
    LKML-Reference: <1260347148-5519-1-git-send-regression-fweisbec@gmail.com>
    Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
    44234adc
perf_event.h 22.8 KB