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drm/i915/hwmon: Fix locking inversion in sysfs getter
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In i915 hwmon sysfs getter path we now take a hwmon_lock, then acquire an
rpm wakeref.  That results in lock inversion:

<4> [197.079335] ======================================================
<4> [197.085473] WARNING: possible circular locking dependency detected
<4> [197.091611] 6.8.0-rc7-Patchwork_129026v7-gc4dc92fb1152+ #1 Not tainted
<4> [197.098096] ------------------------------------------------------
<4> [197.104231] prometheus-node/839 is trying to acquire lock:
<4> [197.109680] ffffffff82764d80 (fs_reclaim){+.+.}-{0:0}, at: __kmalloc+0x9a/0x350
<4> [197.116939]
but task is already holding lock:
<4> [197.122730] ffff88811b772a40 (&hwmon->hwmon_lock){+.+.}-{3:3}, at: hwm_energy+0x4b/0x100 [i915]
<4> [197.131543]
which lock already depends on the new lock.
...
<4> [197.507922] Chain exists of:
  fs_reclaim --> &gt->reset.mutex --> &hwmon->hwmon_lock
<4> [197.518528]  Possible unsafe locking scenario:
<4> [197.524411]        CPU0                    CPU1
<4> [197.528916]        ----                    ----
<4> [197.533418]   lock(&hwmon->hwmon_lock);
<4> [197.537237]                                lock(&gt->reset.mutex);
<4> [197.543376]                                lock(&hwmon->hwmon_lock);
<4> [197.549682]   lock(fs_reclaim);
...
<4> [197.632548] Call Trace:
<4> [197.634990]  <TASK>
<4> [197.637088]  dump_stack_lvl+0x64/0xb0
<4> [197.640738]  check_noncircular+0x15e/0x180
<4> [197.652968]  check_prev_add+0xe9/0xce0
<4> [197.656705]  __lock_acquire+0x179f/0x2300
<4> [197.660694]  lock_acquire+0xd8/0x2d0
<4> [197.673009]  fs_reclaim_acquire+0xa1/0xd0
<4> [197.680478]  __kmalloc+0x9a/0x350
<4> [197.689063]  acpi_ns_internalize_name.part.0+0x4a/0xb0
<4> [197.694170]  acpi_ns_get_node_unlocked+0x60/0xf0
<4> [197.720608]  acpi_ns_get_node+0x3b/0x60
<4> [197.724428]  acpi_get_handle+0x57/0xb0
<4> [197.728164]  acpi_has_method+0x20/0x50
<4> [197.731896]  acpi_pci_set_power_state+0x43/0x120
<4> [197.736485]  pci_power_up+0x24/0x1c0
<4> [197.740047]  pci_pm_default_resume_early+0x9/0x30
<4> [197.744725]  pci_pm_runtime_resume+0x2d/0x90
<4> [197.753911]  __rpm_callback+0x3c/0x110
<4> [197.762586]  rpm_callback+0x58/0x70
<4> [197.766064]  rpm_resume+0x51e/0x730
<4> [197.769542]  rpm_resume+0x267/0x730
<4> [197.773020]  rpm_resume+0x267/0x730
<4> [197.776498]  rpm_resume+0x267/0x730
<4> [197.779974]  __pm_runtime_resume+0x49/0x90
<4> [197.784055]  __intel_runtime_pm_get+0x19/0xa0 [i915]
<4> [197.789070]  hwm_energy+0x55/0x100 [i915]
<4> [197.793183]  hwm_read+0x9a/0x310 [i915]
<4> [197.797124]  hwmon_attr_show+0x36/0x120
<4> [197.800946]  dev_attr_show+0x15/0x60
<4> [197.804509]  sysfs_kf_seq_show+0xb5/0x100

Acquire the wakeref before the lock and hold it as long as the lock is
also held.  Follow that pattern across the whole source file where similar
lock inversion can happen.

v2: Keep hardware read under the lock so the whole operation of updating
    energy from hardware is still atomic (Guenter),
  - instead, acquire the rpm wakeref before the lock and hold it as long
    as the lock is held,
  - use the same aproach for other similar places across the i915_hwmon.c
    source file (Rodrigo).

Fixes: 1b44019 ("drm/i915/guc: Disable PL1 power limit when loading GuC firmware")
Signed-off-by: Janusz Krzysztofik <[email protected]>
Cc: Rodrigo Vivi <[email protected]>
Cc: Guenter Roeck <[email protected]>
Cc: <[email protected]> # v6.5+
Reviewed-by: Ashutosh Dixit <[email protected]>
Reviewed-by: Andi Shyti <[email protected]>
Signed-off-by: Andi Shyti <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
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@jkrzyszt-intel
jkrzyszt-intel authored and Andi Shyti committed Mar 13, 2024
1 parent 79263e4 commit 71b2187
Showing 1 changed file with 19 additions and 18 deletions.
37 changes: 19 additions & 18 deletions drivers/gpu/drm/i915/i915_hwmon.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -72,12 +72,13 @@ hwm_locked_with_pm_intel_uncore_rmw(struct hwm_drvdata *ddat,
struct intel_uncore *uncore = ddat->uncore;
intel_wakeref_t wakeref;

mutex_lock(&hwmon->hwmon_lock);
with_intel_runtime_pm(uncore->rpm, wakeref) {
mutex_lock(&hwmon->hwmon_lock);

with_intel_runtime_pm(uncore->rpm, wakeref)
intel_uncore_rmw(uncore, reg, clear, set);

mutex_unlock(&hwmon->hwmon_lock);
mutex_unlock(&hwmon->hwmon_lock);
}
}

/*
Expand Down Expand Up @@ -136,20 +137,21 @@ hwm_energy(struct hwm_drvdata *ddat, long *energy)
else
rgaddr = hwmon->rg.energy_status_all;

mutex_lock(&hwmon->hwmon_lock);
with_intel_runtime_pm(uncore->rpm, wakeref) {
mutex_lock(&hwmon->hwmon_lock);

with_intel_runtime_pm(uncore->rpm, wakeref)
reg_val = intel_uncore_read(uncore, rgaddr);

if (reg_val >= ei->reg_val_prev)
ei->accum_energy += reg_val - ei->reg_val_prev;
else
ei->accum_energy += UINT_MAX - ei->reg_val_prev + reg_val;
ei->reg_val_prev = reg_val;
if (reg_val >= ei->reg_val_prev)
ei->accum_energy += reg_val - ei->reg_val_prev;
else
ei->accum_energy += UINT_MAX - ei->reg_val_prev + reg_val;
ei->reg_val_prev = reg_val;

*energy = mul_u64_u32_shr(ei->accum_energy, SF_ENERGY,
hwmon->scl_shift_energy);
mutex_unlock(&hwmon->hwmon_lock);
*energy = mul_u64_u32_shr(ei->accum_energy, SF_ENERGY,
hwmon->scl_shift_energy);
mutex_unlock(&hwmon->hwmon_lock);
}
}

static ssize_t
Expand Down Expand Up @@ -404,6 +406,7 @@ hwm_power_max_write(struct hwm_drvdata *ddat, long val)

/* Block waiting for GuC reset to complete when needed */
for (;;) {
wakeref = intel_runtime_pm_get(ddat->uncore->rpm);
mutex_lock(&hwmon->hwmon_lock);

prepare_to_wait(&ddat->waitq, &wait, TASK_INTERRUPTIBLE);
Expand All @@ -417,14 +420,13 @@ hwm_power_max_write(struct hwm_drvdata *ddat, long val)
}

mutex_unlock(&hwmon->hwmon_lock);
intel_runtime_pm_put(ddat->uncore->rpm, wakeref);

schedule();
}
finish_wait(&ddat->waitq, &wait);
if (ret)
goto unlock;

wakeref = intel_runtime_pm_get(ddat->uncore->rpm);
goto exit;

/* Disable PL1 limit and verify, because the limit cannot be disabled on all platforms */
if (val == PL1_DISABLE) {
Expand All @@ -444,9 +446,8 @@ hwm_power_max_write(struct hwm_drvdata *ddat, long val)
intel_uncore_rmw(ddat->uncore, hwmon->rg.pkg_rapl_limit,
PKG_PWR_LIM_1_EN | PKG_PWR_LIM_1, nval);
exit:
intel_runtime_pm_put(ddat->uncore->rpm, wakeref);
unlock:
mutex_unlock(&hwmon->hwmon_lock);
intel_runtime_pm_put(ddat->uncore->rpm, wakeref);
return ret;
}

Expand Down

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