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| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2013-04-19 21:01:24 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2013-04-21 11:21:39 +0200 |
| commit | c79aa0d96548aee50570209eb2d45c8f4ac49230 (patch) | |
| tree | 0b0cc53e2a4b3b37e98b720f0c149a9f074681be | |
| parent | perf/x86: Fix offcore_rsp valid mask for SNB/IVB (diff) | |
| download | linux-c79aa0d96548aee50570209eb2d45c8f4ac49230.tar.xz linux-c79aa0d96548aee50570209eb2d45c8f4ac49230.zip | |
events: Protect access via task_subsys_state_check()
The following RCU splat indicates lack of RCU protection:
[ 953.267649] ===============================
[ 953.267652] [ INFO: suspicious RCU usage. ]
[ 953.267657] 3.9.0-0.rc6.git2.4.fc19.ppc64p7 #1 Not tainted
[ 953.267661] -------------------------------
[ 953.267664] include/linux/cgroup.h:534 suspicious rcu_dereference_check() usage!
[ 953.267669]
[ 953.267669] other info that might help us debug this:
[ 953.267669]
[ 953.267675]
[ 953.267675] rcu_scheduler_active = 1, debug_locks = 0
[ 953.267680] 1 lock held by glxgears/1289:
[ 953.267683] #0: (&sig->cred_guard_mutex){+.+.+.}, at: [<c00000000027f884>] .prepare_bprm_creds+0x34/0xa0
[ 953.267700]
[ 953.267700] stack backtrace:
[ 953.267704] Call Trace:
[ 953.267709] [c0000001f0d1b6e0] [c000000000016e30] .show_stack+0x130/0x200 (unreliable)
[ 953.267717] [c0000001f0d1b7b0] [c0000000001267f8] .lockdep_rcu_suspicious+0x138/0x180
[ 953.267724] [c0000001f0d1b840] [c0000000001d43a4] .perf_event_comm+0x4c4/0x690
[ 953.267731] [c0000001f0d1b950] [c00000000027f6e4] .set_task_comm+0x84/0x1f0
[ 953.267737] [c0000001f0d1b9f0] [c000000000280414] .setup_new_exec+0x94/0x220
[ 953.267744] [c0000001f0d1ba70] [c0000000002f665c] .load_elf_binary+0x58c/0x19b0
...
This commit therefore adds the required RCU read-side critical
section to perf_event_comm().
Reported-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: a.p.zijlstra@chello.nl
Cc: paulus@samba.org
Cc: acme@ghostprotocols.net
Link: http://lkml.kernel.org/r/20130419190124.GA8638@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Gustavo Luiz Duarte <gusld@br.ibm.com>
| -rw-r--r-- | kernel/events/core.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c index 4d3124b39277..9fcb0944f071 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -4596,6 +4596,7 @@ void perf_event_comm(struct task_struct *task) struct perf_event_context *ctx; int ctxn; + rcu_read_lock(); for_each_task_context_nr(ctxn) { ctx = task->perf_event_ctxp[ctxn]; if (!ctx) @@ -4603,6 +4604,7 @@ void perf_event_comm(struct task_struct *task) perf_event_enable_on_exec(ctx); } + rcu_read_unlock(); if (!atomic_read(&nr_comm_events)) return; |