Messages in this thread Patch in this message | | | Date | Thu, 22 Mar 2012 01:43:22 +0200 | Subject | [PATCH] perf: Fix RCU dereference check in perf_event_comm | From | Ari Savolainen <> |
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The warning below is printed when executing a command like sudo perf record su - user -c "echo hello"
It's fixed by moving the call of perf_event_comm to be protected by the task lock.
=============================== [ INFO: suspicious RCU usage. ] 3.3.0 #49 Not tainted ------------------------------- include/linux/cgroup.h:567 suspicious rcu_dereference_check() usage!
other info that might help us debug this:
rcu_scheduler_active = 1, debug_locks = 0 1 lock held by su/3304: #0: (&sig->cred_guard_mutex){+.+.+.}, at: [<ffffffff8117af66>] prepare_bprm_creds+0x36/0x80
stack backtrace: Pid: 3304, comm: su Not tainted 3.3.0 #49 Call Trace: [<ffffffff8109be55>] lockdep_rcu_suspicious+0xe5/0x100 [<ffffffff811131fa>] perf_event_comm+0x37a/0x4d0 [<ffffffff81144525>] ? remove_vma+0x65/0x80 [<ffffffff810722e1>] ? get_parent_ip+0x11/0x50 [<ffffffff814e6fad>] ? sub_preempt_count+0x9d/0xd0 [<ffffffff8117ae05>] set_task_comm+0x75/0x1a0 [<ffffffff8102b945>] ? mmap_rnd+0x45/0x50 [<ffffffff8117b6d2>] setup_new_exec+0xa2/0x340 [<ffffffff811c98f7>] load_elf_binary+0x3c7/0x19d0 [<ffffffff814e3275>] ? _raw_read_unlock+0x35/0x60 [<ffffffff8117a313>] ? search_binary_handler+0x1c3/0x530 [<ffffffff810722e1>] ? get_parent_ip+0x11/0x50 [<ffffffff814e6fad>] ? sub_preempt_count+0x9d/0xd0 [<ffffffff814e6fad>] ? sub_preempt_count+0x9d/0xd0 [<ffffffff811c9530>] ? do_mmap+0x40/0x40 [<ffffffff8117a2f0>] search_binary_handler+0x1a0/0x530 [<ffffffff8117a1a7>] ? search_binary_handler+0x57/0x530 [<ffffffff8117974d>] ? copy_strings.isra.32+0x1fd/0x230 [<ffffffff8117b44f>] do_execve_common.isra.36+0x43f/0x570 [<ffffffff8117b166>] ? do_execve_common.isra.36+0x156/0x570 [<ffffffff81296837>] ? __strncpy_from_user+0x27/0x60 [<ffffffff8117b59b>] do_execve+0x1b/0x20 [<ffffffff8100c317>] sys_execve+0x47/0x70 [<ffffffff814eb39c>] stub_execve+0x6c/0xc0
Signed-off-by: Ari Savolainen <ari.m.savolainen@gmail.com> --- fs/exec.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/fs/exec.c b/fs/exec.c index 153dee1..373ff93 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1067,8 +1067,8 @@ void set_task_comm(struct task_struct *tsk, char *buf) memset(tsk->comm, 0, TASK_COMM_LEN); wmb(); strlcpy(tsk->comm, buf, sizeof(tsk->comm)); - task_unlock(tsk); perf_event_comm(tsk); + task_unlock(tsk); }
static void filename_to_taskname(char *tcomm, const char *fn, unsigned int len) -- 1.7.9.1
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