• Mark Rutland's avatar
    drivers/perf: arm-ccn: don't log to dmesg in event_init · d0a963cf
    Mark Rutland authored
    [ Upstream commit 1898eb61fbc9703efee886d3abec27a388cf28c3 ]
    
    The ARM CCN PMU driver uses dev_warn() to complain about parameters in
    the user-provided perf_event_attr. This means that under normal
    operation (e.g. a single invocation of the perf tool), a number of
    messages warnings may be logged to dmesg.
    
    Tools may issue multiple syscalls to probe for feature support, and
    multiple applications (from multiple users) can attempt to open events
    simultaneously, so this is not very helpful, even if a user happens to
    have access to dmesg. Worse, this can push important information out of
    the dmesg ring buffer, and can significantly slow down syscall fuzzers,
    vastly increasing the time it takes to find critical bugs.
    
    Demote the dev_warn() instances to dev_dbg(), as is the case for all
    other PMU drivers under drivers/perf/. Users who wish to debug PMU event
    initialisation can enable dynamic debug to receive these messages.
    Signed-off-by: 's avatarMark Rutland <mark.rutland@arm.com>
    Cc: Pawel Moll <pawel.moll@arm.com>
    Cc: Will Deacon <will.deacon@arm.com>
    Signed-off-by: 's avatarWill Deacon <will.deacon@arm.com>
    Signed-off-by: 's avatarSasha Levin <alexander.levin@microsoft.com>
    Signed-off-by: 's avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    d0a963cf
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