Thoth-3.9
ARM: perf: simplify __hw_perf_event_init err handling (v2)

Currently __hw_perf_event_init has an err variable that's ignored right
until the end, where it's initialised, conditionally set, and then used
as a boolean flag deciding whether to return another error code.

This patch removes the err variable and simplifies the associated error
handling logic.

Add: ARM: perf: simplify __hw_perf_event_init err handling Currently __hw_perf_event_init has an err variable that's ignored right until the end, where it's initialised, conditionally set, and then used as a boolean flag deciding whether to return another error code.

This patch removes the err variable and simplifies the associated error
handling logic

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: javier Sayago <admin@lonasdigital.com>
ARM: Add optimised swahb32() byteswap helper for v6 and above

ARMv6 and later processors have the REV16 instruction, which swaps
the bytes within each halfword of a register value.

This is already used to implement swab16(), but since the native
operation performaed by REV16 is actually swahb32(), this patch
renames the existing swab16() helper accordingly and defines
__arch_swab16() in terms of it.  This allows calls to both swab16()
and swahb32() to be optimised.

The compiler's generated code might improve someday, but as of
4.5.2 the code generated for pure C implementing these 16-bit
bytesswaps remains pessimal.

swahb32() is useful for converting 32-bit Thumb instructions
between integer and memory representation on BE8 platforms (among
other uses).

Signed-off-by: Dave Martin <dave.martin@linaro.org>
Signed-off-by: Javier Sayago <admin@lonasdigital.com>
cpufreq: Fix sysfs deadlock with concurrent hotplug/frequency
 switch Running one program that continuously hotplugs and replugs a cpu
 concurrently with another program that continuously writes to the
 scaling_set_speed node eventually deadlocks with:

=============================================
[ INFO: possible recursive locking detected ]
3.4.0 #37 Tainted: G        W
---------------------------------------------
filemonkey/122 is trying to acquire lock:
 (s_active#13){++++.+}, at: [<c01a3d28>] sysfs_remove_dir+0x9c/0xb4

but task is already holding lock:
 (s_active#13){++++.+}, at: [<c01a22f0>] sysfs_write_file+0xe8/0x140

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(s_active#13);
  lock(s_active#13);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

2 locks held by filemonkey/122:
 #0:  (&buffer->mutex){+.+.+.}, at: [<c01a2230>] sysfs_write_file+0x28/0x140
 #1:  (s_active#13){++++.+}, at: [<c01a22f0>] sysfs_write_file+0xe8/0x140

stack backtrace:
[<c0014fcc>] (unwind_backtrace+0x0/0x120) from [<c00ca600>] (validate_chain+0x6f8/0x1054)
[<c00ca600>] (validate_chain+0x6f8/0x1054) from [<c00cb778>] (__lock_acquire+0x81c/0x8d8)
[<c00cb778>] (__lock_acquire+0x81c/0x8d8) from [<c00cb9c0>] (lock_acquire+0x18c/0x1e8)
[<c00cb9c0>] (lock_acquire+0x18c/0x1e8) from [<c01a3ba8>] (sysfs_addrm_finish+0xd0/0x180)
[<c01a3ba8>] (sysfs_addrm_finish+0xd0/0x180) from [<c01a3d28>] (sysfs_remove_dir+0x9c/0xb4)
[<c01a3d28>] (sysfs_remove_dir+0x9c/0xb4) from [<c02d0e5c>] (kobject_del+0x10/0x38)
[<c02d0e5c>] (kobject_del+0x10/0x38) from [<c02d0f74>] (kobject_release+0xf0/0x194)
[<c02d0f74>] (kobject_release+0xf0/0x194) from [<c0565a98>] (cpufreq_cpu_put+0xc/0x24)
[<c0565a98>] (cpufreq_cpu_put+0xc/0x24) from [<c05683f0>] (store+0x6c/0x74)
[<c05683f0>] (store+0x6c/0x74) from [<c01a2314>] (sysfs_write_file+0x10c/0x140)
[<c01a2314>] (sysfs_write_file+0x10c/0x140) from [<c014af44>] (vfs_write+0xb0/0x128)
[<c014af44>] (vfs_write+0xb0/0x128) from [<c014b06c>] (sys_write+0x3c/0x68)
[<c014b06c>] (sys_write+0x3c/0x68) from [<c000e0e0>] (ret_fast_syscall+0x0/0x3c)

This is because store() in cpufreq.c indirectly grabs a kobject
with kobject_get() and is the last one to call kobject_put()
indirectly via cpufreq_cpu_put().

Fix this deadlock by introducing two new functions,
cpufreq_cpu_get_sysfs() and cpufreq_cpu_put_sysfs() which do the
same thing as cpufreq_cpu_{get,put}() but don't grab the kobject.

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Javier Sayago <admin@lonasdigital.com>
cpufreq / stats: fix race between stats allocation and first usage

This patch forces complete struct cpufreq_stats allocation for all cpus before
registering CPUFREQ_TRANSITION_NOTIFIER notifier, otherwise in some conditions
cpufreq_stat_notifier_trans() can be called in the middle of stats allocation,
in this case cpufreq_stats_table already exists, but stat->freq_table is NULL.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Javier Sayago <admin@lonasdigital.com>