#!/bin/bash # # Alternate sleeping and spinning on randomly selected CPUs. The purpose # of this script is to inflict random OS jitter on a concurrently running # test. # # Usage: jitter.sh me duration [ sleepmax [ spinmax ] ] # # me: Random-number-generator seed salt. # duration: Time to run in seconds. # sleepmax: Maximum microseconds to sleep, defaults to one second. # spinmax: Maximum microseconds to spin, defaults to one millisecond. # # This program is free software; you can redistribute it and/or modify # it under the terms of the GNU General Public License as published by # the Free Software Foundation; either version 2 of the License, or # (at your option) any later version. # # This program is distributed in the hope that it will be useful, # but WITHOUT ANY WARRANTY; without even the implied warranty of # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the # GNU General Public License for more details. # # You should have received a copy of the GNU General Public License # along with this program; if not, you can access it online at # http://www.gnu.org/licenses/gpl-2.0.html. # # Copyright (C) IBM Corporation, 2016 # # Authors: Paul E. McKenney me=$(($1 * 1000)) duration=$2 sleepmax=${3-1000000} spinmax=${4-1000} n=1 starttime=`awk 'BEGIN { print systime(); }' < /dev/null` while : do # Check for done. t=`awk -v s=$starttime 'BEGIN { print systime() - s; }' < /dev/null` if test "$t" -gt "$duration" then exit 0; fi # Set affinity to randomly selected CPU cpus=`ls /sys/devices/system/cpu/*/online | sed -e 's,/[^/]*$,,' -e 's/^[^0-9]*//' | grep -v '^0*$'` cpumask=`awk -v cpus="$cpus" -v me=$me -v n=$n 'BEGIN { srand(n + me + systime()); ncpus = split(cpus, ca); curcpu = ca[int(rand() * ncpus + 1)]; mask = lshift(1, curcpu); if (mask + 0 <= 0) mask = 1; printf("%#x\n", mask); }' < /dev/null` n=$(($n+1)) if ! taskset -p $cpumask $$ > /dev/null 2>&1 then echo taskset failure: '"taskset -p ' $cpumask $$ '"' exit 1 fi # Sleep a random duration sleeptime=`awk -v me=$me -v n=$n -v sleepmax=$sleepmax 'BEGIN { srand(n + me + systime()); printf("%06d", int(rand() * sleepmax)); }' < /dev/null` n=$(($n+1)) sleep .$sleeptime # Spin a random duration limit=`awk -v me=$me -v n=$n -v spinmax=$spinmax 'BEGIN { srand(n + me + systime()); printf("%06d", int(rand() * spinmax)); }' < /dev/null` n=$(($n+1)) for i in {1..$limit} do echo > /dev/null done done exit 1 me='qt'>
path: root/tools/build/feature/test-libelf-getphdrnum.c
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authorDouglas Miller <dougmill@linux.vnet.ibm.com>2017-01-28 06:42:20 -0600
committerTejun Heo <tj@kernel.org>2017-01-28 07:49:42 -0500
commit966d2b04e070bc040319aaebfec09e0144dc3341 (patch)
tree4b96156e3d1dd4dfd6039b7c219c9dc4616da52d /tools/build/feature/test-libelf-getphdrnum.c
parent1b1bc42c1692e9b62756323c675a44cb1a1f9dbd (diff)
percpu-refcount: fix reference leak during percpu-atomic transition
percpu_ref_tryget() and percpu_ref_tryget_live() should return "true" IFF they acquire a reference. But the return value from atomic_long_inc_not_zero() is a long and may have high bits set, e.g. PERCPU_COUNT_BIAS, and the return value of the tryget routines is bool so the reference may actually be acquired but the routines return "false" which results in a reference leak since the caller assumes it does not need to do a corresponding percpu_ref_put(). This was seen when performing CPU hotplug during I/O, as hangs in blk_mq_freeze_queue_wait where percpu_ref_kill (blk_mq_freeze_queue_start) raced with percpu_ref_tryget (blk_mq_timeout_work). Sample stack trace: __switch_to+0x2c0/0x450 __schedule+0x2f8/0x970 schedule+0x48/0xc0 blk_mq_freeze_queue_wait+0x94/0x120 blk_mq_queue_reinit_work+0xb8/0x180 blk_mq_queue_reinit_prepare+0x84/0xa0 cpuhp_invoke_callback+0x17c/0x600 cpuhp_up_callbacks+0x58/0x150 _cpu_up+0xf0/0x1c0 do_cpu_up+0x120/0x150 cpu_subsys_online+0x64/0xe0 device_online+0xb4/0x120 online_store+0xb4/0xc0 dev_attr_store+0x68/0xa0 sysfs_kf_write+0x80/0xb0 kernfs_fop_write+0x17c/0x250 __vfs_write+0x6c/0x1e0 vfs_write+0xd0/0x270 SyS_write+0x6c/0x110 system_call+0x38/0xe0 Examination of the queue showed a single reference (no PERCPU_COUNT_BIAS, and __PERCPU_REF_DEAD, __PERCPU_REF_ATOMIC set) and no requests. However, conditions at the time of the race are count of PERCPU_COUNT_BIAS + 0 and __PERCPU_REF_DEAD and __PERCPU_REF_ATOMIC set. The fix is to make the tryget routines use an actual boolean internally instead of the atomic long result truncated to a int. Fixes: e625305b3907 percpu-refcount: make percpu_ref based on longs instead of ints Link: https://bugzilla.kernel.org/show_bug.cgi?id=190751 Signed-off-by: Douglas Miller <dougmill@linux.vnet.ibm.com> Reviewed-by: Jens Axboe <axboe@fb.com> Signed-off-by: Tejun Heo <tj@kernel.org> Fixes: e625305b3907 ("percpu-refcount: make percpu_ref based on longs instead of ints") Cc: stable@vger.kernel.org # v3.18+
Diffstat (limited to 'tools/build/feature/test-libelf-getphdrnum.c')