/* * POWER Data Stream Control Register (DSCR) fork test * * This testcase modifies the DSCR using mtspr, forks and then * verifies that the child process has the correct changed DSCR * value using mfspr. * * When using the privilege state SPR, the instructions such as * mfspr or mtspr are priviledged and the kernel emulates them * for us. Instructions using problem state SPR can be exuecuted * directly without any emulation if the HW supports them. Else * they also get emulated by the kernel. * * Copyright 2012, Anton Blanchard, IBM Corporation. * Copyright 2015, Anshuman Khandual, IBM Corporation. * * This program is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 as published * by the Free Software Foundation. */ #include "dscr.h" int dscr_inherit(void) { unsigned long i, dscr = 0; pid_t pid; srand(getpid()); set_dscr(dscr); for (i = 0; i < COUNT; i++) { unsigned long cur_dscr, cur_dscr_usr; dscr++; if (dscr > DSCR_MAX) dscr = 0; if (i % 2 == 0) set_dscr_usr(dscr); else set_dscr(dscr); pid = fork(); if (pid == -1) { perror("fork() failed"); exit(1); } else if (pid) { int status; if (waitpid(pid, &status, 0) == -1) { perror("waitpid() failed"); exit(1); } if (!WIFEXITED(status)) { fprintf(stderr, "Child didn't exit cleanly\n"); exit(1); } if (WEXITSTATUS(status) != 0) { fprintf(stderr, "Child didn't exit cleanly\n"); return 1; } } else { cur_dscr = get_dscr(); if (cur_dscr != dscr) { fprintf(stderr, "Kernel DSCR should be %ld " "but is %ld\n", dscr, cur_dscr); exit(1); } cur_dscr_usr = get_dscr_usr(); if (cur_dscr_usr != dscr) { fprintf(stderr, "User DSCR should be %ld " "but is %ld\n", dscr, cur_dscr_usr); exit(1); } exit(0); } } return 0; } int main(int argc, char *argv[]) { return test_harness(dscr_inherit, "dscr_inherit_test"); } 'active' href='/cgit.cgi/linux/net-next.git/commit/net/mac80211/mesh_hwmp.c?h=nds-private-remove&id=966d2b04e070bc040319aaebfec09e0144dc3341'>commitdiff
path: root/net/mac80211/mesh_hwmp.c
diff options
context:
space:
mode:
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 /net/mac80211/mesh_hwmp.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 'net/mac80211/mesh_hwmp.c')