linux-kernel - Re: [PATCH] perf: Protect pmu device removal with pmu_bus_running check CONFIG_DEBUG_TEST_DRIVER

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Message-ID: <1110984561.1204029.1476973829969.JavaMail.zimbra@redhat.com>
Date:   Thu, 20 Oct 2016 10:30:29 -0400 (EDT)
From:   CAI Qian <caiqian@...hat.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Rob Herring <robh@...nel.org>, Kan Liang <kan.liang@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH] perf: Protect pmu device removal with pmu_bus_running
 check CONFIG_DEBUG_TEST_DRIVER_REMOVE kernel panic


> CAI Qian reported crash [1] in uncore device removal related
> to CONFIG_DEBUG_TEST_DRIVER_REMOVE option.
> 
> The reason for crash is that  perf_pmu_unregister tries to remove
> pmu device which is not added at this point. We add pmu devices
> only after pmu_bus is registered which happens in perf_event_sysfs_init
> init call and sets pmu_bus_running flag.
> 
> The fix is to get the pmu_bus_running flag state at the point
> the pmu is taken  out of the pmus list and  remove the device
> later only if it's set.
> 
> [1] https://marc.info/?l=linux-kernel&m=147688837328451
> 
> Reported-by: CAI Qian <caiqian@...hat.com>
> Signed-off-by: Jiri Olsa <jolsa@...nel.org>

Tested-by: CAI Qian <caiqian@...hat.com>