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b6ffdf27f3
Function __hw_perf_event_init() used a CPU variable without
ensuring CPU preemption has been disabled. This caused the
following warning in the kernel log:
[ 7.277085] BUG: using smp_processor_id() in preemptible
[00000000] code: cf-csdiag/1892
[ 7.277111] caller is cf_diag_event_init+0x13a/0x338
[ 7.277122] CPU: 10 PID: 1892 Comm: cf-csdiag Not tainted
5.0.0-20190318.rc0.git0.9e1a11e0f602.300.fc29.s390x+debug #1
[ 7.277131] Hardware name: IBM 2964 NC9 712 (LPAR)
[ 7.277139] Call Trace:
[ 7.277150] ([<000000000011385a>] show_stack+0x82/0xd0)
[ 7.277161] [<0000000000b7a71a>] dump_stack+0x92/0xd0
[ 7.277174] [<00000000007b7e9c>] check_preemption_disabled+0xe4/0x100
[ 7.277183] [<00000000001228aa>] cf_diag_event_init+0x13a/0x338
[ 7.277195] [<00000000002cf3aa>] perf_try_init_event+0x72/0xf0
[ 7.277204] [<00000000002d0bba>] perf_event_alloc+0x6fa/0xce0
[ 7.277214] [<00000000002dc4a8>] __s390x_sys_perf_event_open+0x398/0xd50
[ 7.277224] [<0000000000b9e8f0>] system_call+0xdc/0x2d8
[ 7.277233] 2 locks held by cf-csdiag/1892:
[ 7.277241] #0: 00000000976f5510 (&sig->cred_guard_mutex){+.+.},
at: __s390x_sys_perf_event_open+0xd2e/0xd50
[ 7.277257] #1: 00000000363b11bd (&pmus_srcu){....},
at: perf_event_alloc+0x52e/0xce0
The variable is now accessed in proper context. Use
get_cpu_var()/put_cpu_var() pair to disable
preemption during access.
As the hardware authorization settings apply to all CPUs, it
does not matter which CPU is used to check the authorization setting.
Remove the event->count assignment. It is not needed as function
perf_event_alloc() allocates memory for the event with kzalloc() and
thus count is already set to zero.
Fixes: fe5908bccc ("s390/cpum_cf_diag: Add support for s390 counter facility diagnostic trace")
Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Reviewed-by: Hendrik Brueckner <brueckner@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.