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Subject[PATCH 4.4 054/131] coresight: fixing lockdep error
Date
4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

[ Upstream commit a9ddc71f5840c2711e530f2e055b278f79948b29 ]

On some platform the following lockdep error occurs when doing simple
manipulations:

[ 23.197021]
[ 23.198608] ======================================================
[ 23.205078] [ INFO: possible circular locking dependency detected ]
[ 23.211639] 4.4.0-rc8-00025-gbbf360b #172 Not tainted
[ 23.216918] -------------------------------------------------------
[ 23.223480] sh/858 is trying to acquire lock:
[ 23.228057] (coresight_mutex){+.+.+.}, at: [<c0415d40>] coresight_enable+0x1c/0x1b4
[ 23.236206]
[ 23.236206] but task is already holding lock:
[ 23.242309] (s_active#52){++++.+}, at: [<c01d4b40>] kernfs_fop_write+0x5c/0x1c0
[ 23.250122]
[ 23.250122] which lock already depends on the new lock.
[ 23.250122]
[ 23.258697]
[ 23.258697] the existing dependency chain (in reverse order) is:
[ 23.266510]
-> #1 (s_active#52){++++.+}:
[ 23.270843] [<c01d30ec>] __kernfs_remove+0x294/0x35c
[ 23.276672] [<c01d3e44>] kernfs_remove_by_name_ns+0x44/0x8c
[ 23.283172] [<c01d6318>] remove_files+0x3c/0x84
[ 23.288543] [<c01d66b4>] sysfs_remove_group+0x48/0x9c
[ 23.294494] [<c01d6734>] sysfs_remove_groups+0x2c/0x3c
[ 23.300506] [<c030b658>] device_remove_attrs+0x5c/0x74
[ 23.306549] [<c030c290>] device_del+0x110/0x218
[ 23.311950] [<c030c3c4>] device_unregister+0x2c/0x6c
[ 23.317779] [<c04156d8>] coresight_unregister+0x30/0x40
[ 23.323883] [<c041a290>] etm_probe+0x228/0x2e8
[ 23.329193] [<c02bc760>] amba_probe+0xe4/0x160
[ 23.334503] [<c0310540>] driver_probe_device+0x23c/0x480
[ 23.340728] [<c0310820>] __driver_attach+0x9c/0xa0
[ 23.346374] [<c030e400>] bus_for_each_dev+0x70/0xa4
[ 23.352142] [<c030fcf4>] driver_attach+0x24/0x28
[ 23.357604] [<c030f86c>] bus_add_driver+0x1e0/0x278
[ 23.363372] [<c0310d48>] driver_register+0x80/0x100
[ 23.369110] [<c02bc508>] amba_driver_register+0x58/0x5c
[ 23.375244] [<c0749514>] etm_driver_init+0x18/0x1c
[ 23.380889] [<c0009918>] do_one_initcall+0xc4/0x20c
[ 23.386657] [<c0715e7c>] kernel_init_freeable+0x160/0x208
[ 23.392974] [<c052d7fc>] kernel_init+0x18/0xf0
[ 23.398254] [<c0010850>] ret_from_fork+0x14/0x24
[ 23.403747]
-> #0 (coresight_mutex){+.+.+.}:
[ 23.408447] [<c008ed60>] lock_acquire+0xe4/0x210
[ 23.413909] [<c0530a30>] mutex_lock_nested+0x74/0x450
[ 23.419860] [<c0415d40>] coresight_enable+0x1c/0x1b4
[ 23.425689] [<c0416030>] enable_source_store+0x58/0x68
[ 23.431732] [<c030b358>] dev_attr_store+0x20/0x2c
[ 23.437286] [<c01d55e8>] sysfs_kf_write+0x50/0x54
[ 23.442871] [<c01d4ba8>] kernfs_fop_write+0xc4/0x1c0
[ 23.448699] [<c015b60c>] __vfs_write+0x34/0xe4
[ 23.454040] [<c015bf38>] vfs_write+0x98/0x174
[ 23.459228] [<c015c7a8>] SyS_write+0x4c/0xa8
[ 23.464355] [<c00107c0>] ret_fast_syscall+0x0/0x1c
[ 23.470031]
[ 23.470031] other info that might help us debug this:
[ 23.470031]
[ 23.478393] Possible unsafe locking scenario:
[ 23.478393]
[ 23.484619] CPU0 CPU1
[ 23.489349] ---- ----
[ 23.494079] lock(s_active#52);
[ 23.497497] lock(coresight_mutex);
[ 23.503906] lock(s_active#52);
[ 23.509918] lock(coresight_mutex);
[ 23.513702]
[ 23.513702] *** DEADLOCK ***
[ 23.513702]
[ 23.519897] 3 locks held by sh/858:
[ 23.523529] #0: (sb_writers#7){.+.+.+}, at: [<c015ec38>] __sb_start_write+0xa8/0xd4
[ 23.531799] #1: (&of->mutex){+.+...}, at: [<c01d4b38>] kernfs_fop_write+0x54/0x1c0
[ 23.539916] #2: (s_active#52){++++.+}, at: [<c01d4b40>] kernfs_fop_write+0x5c/0x1c0
[ 23.548156]
[ 23.548156] stack backtrace:
[ 23.552734] CPU: 0 PID: 858 Comm: sh Not tainted 4.4.0-rc8-00025-gbbf360b #172
[ 23.560302] Hardware name: Generic OMAP4 (Flattened Device Tree)
[ 23.566589] Backtrace:
[ 23.569152] [<c00154d4>] (dump_backtrace) from [<c00156d0>] (show_stack+0x18/0x1c)
[ 23.577087] r7:ed4b8570 r6:c0936400 r5:c07ae71c r4:00000000
[ 23.583038] [<c00156b8>] (show_stack) from [<c027e69c>] (dump_stack+0x98/0xc0)
[ 23.590606] [<c027e604>] (dump_stack) from [<c008a750>] (print_circular_bug+0x21c/0x33c)
[ 23.599090] r5:c0939d60 r4:c0936400
[ 23.602874] [<c008a534>] (print_circular_bug) from [<c008e370>] (__lock_acquire+0x1c98/0x1d88)
[ 23.611877] r10:00000003 r9:c0fd7a5c r8:ed4b8550 r7:ed4b8570 r6:ed4b8000 r5:c0ff69e4
[ 23.620117] r4:c0936400 r3:ed4b8550
[ 23.623901] [<c008c6d8>] (__lock_acquire) from [<c008ed60>] (lock_acquire+0xe4/0x210)
[ 23.632080] r10:00000000 r9:00000000 r8:60000013 r7:c07cb7b4 r6:00000001 r5:00000000
[ 23.640350] r4:00000000
[ 23.643005] [<c008ec7c>] (lock_acquire) from [<c0530a30>] (mutex_lock_nested+0x74/0x450)
[ 23.651458] r10:ecc0bf80 r9:edbe7dcc r8:ed4b8000 r7:c0fd7a5c r6:c0415d40 r5:00000000
[ 23.659729] r4:c07cb780
[ 23.662384] [<c05309bc>] (mutex_lock_nested) from [<c0415d40>] (coresight_enable+0x1c/0x1b4)
[ 23.671234] r10:ecc0bf80 r9:edbe7dcc r8:ed733c00 r7:00000000 r6:ed733c00 r5:00000002
[ 23.679473] r4:ed762140
[ 23.682128] [<c0415d24>] (coresight_enable) from [<c0416030>] (enable_source_store+0x58/0x68)
[ 23.691070] r7:00000000 r6:ed733c00 r5:00000002 r4:ed762160
[ 23.697052] [<c0415fd8>] (enable_source_store) from [<c030b358>] (dev_attr_store+0x20/0x2c)
[ 23.705780] r5:edbe7dc0 r4:c0415fd8
[ 23.709533] [<c030b338>] (dev_attr_store) from [<c01d55e8>] (sysfs_kf_write+0x50/0x54)
[ 23.717834] r5:edbe7dc0 r4:c030b338
[ 23.721618] [<c01d5598>] (sysfs_kf_write) from [<c01d4ba8>] (kernfs_fop_write+0xc4/0x1c0)
[ 23.730163] r7:00000000 r6:00000000 r5:00000002 r4:edbe7dc0
[ 23.736145] [<c01d4ae4>] (kernfs_fop_write) from [<c015b60c>] (__vfs_write+0x34/0xe4)
[ 23.744323] r10:00000000 r9:ecc0a000 r8:c0010964 r7:ecc0bf80 r6:00000002 r5:c01d4ae4
[ 23.752593] r4:ee385a40
[ 23.755249] [<c015b5d8>] (__vfs_write) from [<c015bf38>] (vfs_write+0x98/0x174)
[ 23.762908] r9:ecc0a000 r8:c0010964 r7:ecc0bf80 r6:000ab0d8 r5:00000002 r4:ee385a40
[ 23.771057] [<c015bea0>] (vfs_write) from [<c015c7a8>] (SyS_write+0x4c/0xa8)
[ 23.778442] r8:c0010964 r7:00000002 r6:000ab0d8 r5:ee385a40 r4:ee385a40
[ 23.785522] [<c015c75c>] (SyS_write) from [<c00107c0>] (ret_fast_syscall+0x0/0x1c)
[ 23.793457] r7:00000004 r6:00000001 r5:000ab0d8 r4:00000002
[ 23.799652] coresight-etb10 54162000.etb: ETB enabled
[ 23.805084] coresight-funnel 54164000.funnel: FUNNEL inport 0 enabled
[ 23.811859] coresight-replicator 44000000.ocp:replicator: REPLICATOR enabled
[ 23.819335] coresight-funnel 54158000.funnel: FUNNEL inport 0 enabled
[ 23.826110] coresight-etm3x 5414c000.ptm: ETM tracing enabled

The locking in coresight_unregister() is not required as the only customers of
the function are drivers themselves when an initialisation failure has been
encoutered.

Reported-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: Mathieu Poirier <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.c | 4 ----
1 file changed, 4 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight.c b/drivers/hwtracing/coresight/coresight.c
index 902ee6efd09c..84fc60318f79 100644
--- a/drivers/hwtracing/coresight/coresight.c
+++ b/drivers/hwtracing/coresight/coresight.c
@@ -716,12 +716,8 @@ EXPORT_SYMBOL_GPL(coresight_register);

void coresight_unregister(struct coresight_device *csdev)
{
- mutex_lock(&coresight_mutex);
-
kfree(csdev->conns);
device_unregister(&csdev->dev);
-
- mutex_unlock(&coresight_mutex);
}
EXPORT_SYMBOL_GPL(coresight_unregister);

--
2.19.1


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