Remove unnecessary locking in the 'for_each' iterators. Any locking should
be taken care of by using hwmod API functions in the functions called by the
iterators.
In addition, having locking here causes lockdep to detect possible circular
dependencies (originally reported by Partha Basak <p-basak2@xxxxxx>.)
For example, during init (#0 below) you have the hwmod_mutex acquired
(hwmod_for_each_by_class()) then the dpm_list_mtx acquired
(device_pm_add()). Later, during suspend the dpm_list_mtx is aquired
first (dpm_suspend_noirq()), then the omap_hwmod_mutex is acquired
(omap_hwmod_idle()).
[ 810.170593] =======================================================
[ 810.170593] [ INFO: possible circular locking dependency detected ]
[ 810.170623] 2.6.35-rc5-00131-g56e767c-dirty #34
[ 810.170654] -------------------------------------------------------
[ 810.170654] sh/670 is trying to acquire lock:
[ 810.170684] (omap_hwmod_mutex){+.+.+.}, at: [<c004fe84>] omap_hwmod_idle+0x1c/0x38
[ 810.170745]
[ 810.170745] but task is already holding lock:
[ 810.170776] (dpm_list_mtx){+.+...}, at: [<c023baf8>] dpm_suspend_noirq+0x28/0x188
[ 810.170806]
[ 810.170837] which lock already depends on the new lock.
[ 810.170837]
[ 810.170837]
[ 810.170837] the existing dependency chain (in reverse order) is:
[ 810.170867]
[ 810.170867] -> #1 (dpm_list_mtx){+.+...}:
[ 810.170898] [<c009bc3c>] lock_acquire+0x60/0x74
[ 810.170959] [<c0437a9c>] mutex_lock_nested+0x58/0x2e4
[ 810.170989] [<c023bcc0>] device_pm_add+0x14/0xcc
[ 810.171020] [<c0235304>] device_add+0x3b8/0x564
[ 810.171051] [<c0238834>] platform_device_add+0x104/0x160
[ 810.171112] [<c005f2a8>] omap_device_build_ss+0x14c/0x1c8
[ 810.171142] [<c005f36c>] omap_device_build+0x48/0x50
[ 810.171173] [<c004d34c>] omap2_init_gpio+0xf0/0x15c
[ 810.171203] [<c004f254>] omap_hwmod_for_each_by_class+0x60/0xa4
[ 810.171264] [<c0040340>] do_one_initcall+0x58/0x1b4
[ 810.171295] [<c0008574>] kernel_init+0x98/0x150
[ 810.171325] [<c0041968>] kernel_thread_exit+0x0/0x8
[ 810.171356]
[ 810.171356] -> #0 (omap_hwmod_mutex){+.+.+.}:
[ 810.171386] [<c009b4e4>] __lock_acquire+0x108c/0x1784
[ 810.171447] [<c009bc3c>] lock_acquire+0x60/0x74
[ 810.171478] [<c0437a9c>] mutex_lock_nested+0x58/0x2e4
[ 810.171508] [<c004fe84>] omap_hwmod_idle+0x1c/0x38
[ 810.171539] [<c005eb9c>] omap_device_idle_hwmods+0x20/0x3c
[ 810.171600] [<c005ec88>] _omap_device_deactivate+0x58/0x14c
[ 810.171630] [<c005ef50>] omap_device_idle+0x4c/0x6c
[ 810.171661] [<c0053e7c>] platform_pm_runtime_suspend+0x4c/0x74
[ 810.171691] [<c023c9f8>] __pm_runtime_suspend+0x204/0x34c
[ 810.171722] [<c023cbe0>] pm_runtime_suspend+0x20/0x34
[ 810.171752] [<c0053dbc>] platform_pm_runtime_idle+0x8/0x10
[ 810.171783] [<c023c344>] __pm_runtime_idle+0x15c/0x198
[ 810.171813] [<c023c3f8>] pm_runtime_idle+0x1c/0x30
[ 810.171844] [<c0053dac>] platform_pm_suspend_noirq+0x48/0x50
[ 810.171875] [<c023ad4c>] pm_noirq_op+0xa0/0x184
[ 810.171905] [<c023bb7c>] dpm_suspend_noirq+0xac/0x188
[ 810.171936] [<c00a5d00>] suspend_devices_and_enter+0x94/0x1d8
[ 810.171966] [<c00a5f00>] enter_state+0xbc/0x120
[ 810.171997] [<c00a5654>] state_store+0xa4/0xb8
[ 810.172027] [<c01ea9e0>] kobj_attr_store+0x18/0x1c
[ 810.172088] [<c0129acc>] sysfs_write_file+0x10c/0x144
[ 810.172119] [<c00df83c>] vfs_write+0xb0/0x148
[ 810.172149] [<c00df984>] sys_write+0x3c/0x68
[ 810.172180] [<c0040920>] ret_fast_syscall+0x0/0x3c
[ 810.172210]
[ 810.172210] other info that might help us debug this:
[ 810.172210]
[ 810.172241] 4 locks held by sh/670:
[ 810.172241] #0: (&buffer->mutex){+.+.+.}, at: [<c01299e8>] sysfs_write_file+0x28/0x144
[ 810.172302] #1: (s_active#5){.+.+.+}, at: [<c0129aa8>] sysfs_write_file+0xe8/0x144
[ 810.172363] #2: (pm_mutex){+.+.+.}, at: [<c00a5e64>] enter_state+0x20/0x120
[ 810.172393] #3: (dpm_list_mtx){+.+...}, at: [<c023baf8>] dpm_suspend_noirq+0x28/0x188
Tested-by: Partha Basak <p-basak2@xxxxxx>
Signed-off-by: Kevin Hilman <khilman@xxxxxxxxxxxxxxxxxxx>
---
arch/arm/mach-omap2/omap_hwmod.c | 6 ------
1 files changed, 0 insertions(+), 6 deletions(-)
diff --git a/arch/arm/mach-omap2/omap_hwmod.c b/arch/arm/mach-omap2/omap_hwmod.c
index cb911d7..5941d5b 100644
--- a/arch/arm/mach-omap2/omap_hwmod.c
+++ b/arch/arm/mach-omap2/omap_hwmod.c
@@ -1204,13 +1204,11 @@ int omap_hwmod_for_each(int (*fn)(struct omap_hwmod *oh, void *data),
if (!fn)
return -EINVAL;
- mutex_lock(&omap_hwmod_mutex);
list_for_each_entry(temp_oh, &omap_hwmod_list, node) {
ret = (*fn)(temp_oh, data);
if (ret)
break;
}
- mutex_unlock(&omap_hwmod_mutex);
return ret;
}
@@ -1703,8 +1701,6 @@ int omap_hwmod_for_each_by_class(const char *classname,
pr_debug("omap_hwmod: %s: looking for modules of class %s\n",
__func__, classname);
- mutex_lock(&omap_hwmod_mutex);
-
list_for_each_entry(temp_oh, &omap_hwmod_list, node) {
if (!strcmp(temp_oh->class->name, classname)) {
pr_debug("omap_hwmod: %s: %s: calling callback fn\n",
@@ -1715,8 +1711,6 @@ int omap_hwmod_for_each_by_class(const char *classname,
}
}
- mutex_unlock(&omap_hwmod_mutex);
-
if (ret)
pr_debug("omap_hwmod: %s: iterator terminated early: %d\n",
__func__, ret);
--
1.7.2.1
--
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