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    Subject[PATCH 5.9 277/757] coresight: cti: Write regsiters directly in cti_enable_hw()
    Date
    From: Tingwei Zhang <tingwei@codeaurora.org>

    [ Upstream commit 984f37efa3857dcefa649fbdf64abb94591935c3 ]

    Deadlock as below is triggered by one CPU holds drvdata->spinlock
    and calls cti_enable_hw(). Smp_call_function_single() is called
    in cti_enable_hw() and tries to let another CPU write CTI registers.
    That CPU is trying to get drvdata->spinlock in cti_cpu_pm_notify()
    and doesn't response to IPI from smp_call_function_single().

    [ 988.335937] CPU: 6 PID: 10258 Comm: sh Tainted: G W L
    5.8.0-rc6-mainline-16783-gc38daa79b26b-dirty #1
    [ 988.346364] Hardware name: Thundercomm Dragonboard 845c (DT)
    [ 988.352073] pstate: 20400005 (nzCv daif +PAN -UAO BTYPE=--)
    [ 988.357689] pc : smp_call_function_single+0x158/0x1b8
    [ 988.362782] lr : smp_call_function_single+0x124/0x1b8
    ...
    [ 988.451638] Call trace:
    [ 988.454119] smp_call_function_single+0x158/0x1b8
    [ 988.458866] cti_enable+0xb4/0xf8 [coresight_cti]
    [ 988.463618] coresight_control_assoc_ectdev+0x6c/0x128 [coresight]
    [ 988.469855] coresight_enable+0x1f0/0x364 [coresight]
    [ 988.474957] enable_source_store+0x5c/0x9c [coresight]
    [ 988.480140] dev_attr_store+0x14/0x28
    [ 988.483839] sysfs_kf_write+0x38/0x4c
    [ 988.487532] kernfs_fop_write+0x1c0/0x2b0
    [ 988.491585] vfs_write+0xfc/0x300
    [ 988.494931] ksys_write+0x78/0xe0
    [ 988.498283] __arm64_sys_write+0x18/0x20
    [ 988.502240] el0_svc_common+0x98/0x160
    [ 988.506024] do_el0_svc+0x78/0x80
    [ 988.509377] el0_sync_handler+0xd4/0x270
    [ 988.513337] el0_sync+0x164/0x180

    This change write CTI registers directly in cti_enable_hw().
    Config->hw_powered has been checked to be true with spinlock holded.
    CTI is powered and can be programmed until spinlock is released.

    Fixes: 6a0953ce7de9 ("coresight: cti: Add CPU idle pm notifer to CTI devices")
    Signed-off-by: Tingwei Zhang <tingwei@codeaurora.org>
    [Re-ordered variable declaration]
    Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
    Link: https://lore.kernel.org/r/20200916191737.4001561-10-mathieu.poirier@linaro.org
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/hwtracing/coresight/coresight-cti.c | 24 +++++----------------
    1 file changed, 5 insertions(+), 19 deletions(-)

    diff --git a/drivers/hwtracing/coresight/coresight-cti.c b/drivers/hwtracing/coresight/coresight-cti.c
    index c4e9cc7034ab7..47f3c9abae303 100644
    --- a/drivers/hwtracing/coresight/coresight-cti.c
    +++ b/drivers/hwtracing/coresight/coresight-cti.c
    @@ -86,22 +86,16 @@ void cti_write_all_hw_regs(struct cti_drvdata *drvdata)
    CS_LOCK(drvdata->base);
    }

    -static void cti_enable_hw_smp_call(void *info)
    -{
    - struct cti_drvdata *drvdata = info;
    -
    - cti_write_all_hw_regs(drvdata);
    -}
    -
    /* write regs to hardware and enable */
    static int cti_enable_hw(struct cti_drvdata *drvdata)
    {
    struct cti_config *config = &drvdata->config;
    struct device *dev = &drvdata->csdev->dev;
    + unsigned long flags;
    int rc = 0;

    pm_runtime_get_sync(dev->parent);
    - spin_lock(&drvdata->spinlock);
    + spin_lock_irqsave(&drvdata->spinlock, flags);

    /* no need to do anything if enabled or unpowered*/
    if (config->hw_enabled || !config->hw_powered)
    @@ -112,19 +106,11 @@ static int cti_enable_hw(struct cti_drvdata *drvdata)
    if (rc)
    goto cti_err_not_enabled;

    - if (drvdata->ctidev.cpu >= 0) {
    - rc = smp_call_function_single(drvdata->ctidev.cpu,
    - cti_enable_hw_smp_call,
    - drvdata, 1);
    - if (rc)
    - goto cti_err_not_enabled;
    - } else {
    - cti_write_all_hw_regs(drvdata);
    - }
    + cti_write_all_hw_regs(drvdata);

    config->hw_enabled = true;
    atomic_inc(&drvdata->config.enable_req_count);
    - spin_unlock(&drvdata->spinlock);
    + spin_unlock_irqrestore(&drvdata->spinlock, flags);
    return rc;

    cti_state_unchanged:
    @@ -132,7 +118,7 @@ static int cti_enable_hw(struct cti_drvdata *drvdata)

    /* cannot enable due to error */
    cti_err_not_enabled:
    - spin_unlock(&drvdata->spinlock);
    + spin_unlock_irqrestore(&drvdata->spinlock, flags);
    pm_runtime_put(dev->parent);
    return rc;
    }
    --
    2.25.1


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