From: Heiko Carstens Date: Tue, 26 May 2009 15:28:02 +0000 (+0200) Subject: trace: disable preemption before taking raw spinlocks X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=5b6045a906f48d37591365c5dcdd6d1d146bfd4a;p=openwrt%2Fstaging%2Fblogic.git trace: disable preemption before taking raw spinlocks s390 code uses smp_processor_id() in __raw_spin_lock() code which reveals that a (raw) spinlock is taken without preemption disabled. This can potentially deadlock. To fix this explicitly disable and enable preemption. BUG: using smp_processor_id() in preemptible [00000000] code: cat/2278 caller is trace_find_cmdline+0x40/0xfc CPU: 0 Not tainted 2.6.30-rc7-dirty #39 Process cat (pid: 2278, task: 000000003faedb68, ksp: 000000003b33b988) 000000003b33b988 000000003b33bae0 0000000000000002 0000000000000000 000000003b33bb80 000000003b33baf8 000000003b33baf8 00000000000175d6 0000000000000001 000000003b33b988 000000003f9b0000 000000000000000b 000000000000000c 000000003b33bb40 000000003b33bae0 0000000000000000 0000000000000000 00000000000175d6 000000003b33bae0 000000003b33bb28 Call Trace: ([<00000000000174b2>] show_trace+0x112/0x170) [<0000000000017582>] show_stack+0x72/0x100 [<0000000000441538>] dump_stack+0xc8/0xd8 [<000000000025c350>] debug_smp_processor_id+0x114/0x130 [<00000000000bf0e4>] trace_find_cmdline+0x40/0xfc [<00000000000c35d4>] trace_print_context+0x58/0xac [<00000000000bb676>] print_trace_line+0x416/0x470 [<00000000000bc8fe>] s_show+0x4e/0x428 [<000000000013834e>] seq_read+0x36a/0x5d4 [<0000000000112a78>] vfs_read+0xc8/0x174 [<0000000000112c58>] SyS_read+0x74/0xc4 [<000000000002c7ae>] sysc_noemu+0x10/0x16 [<000002000012436c>] 0x2000012436c 1 lock held by cat/2278: #0: (&p->lock){+.+.+.}, at: [<0000000000138056>] seq_read+0x72/0x5d4 [ Impact: fix preempt-unsafe raw spinlock ] Signed-off-by: Heiko Carstens Acked-by: Steven Rostedt Signed-off-by: Frederic Weisbecker --- diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 02d32baa23ac..a3a8a87d7e91 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -808,6 +808,7 @@ void trace_find_cmdline(int pid, char comm[]) return; } + preempt_disable(); __raw_spin_lock(&trace_cmdline_lock); map = map_pid_to_cmdline[pid]; if (map != NO_CMDLINE_MAP) @@ -816,6 +817,7 @@ void trace_find_cmdline(int pid, char comm[]) strcpy(comm, "<...>"); __raw_spin_unlock(&trace_cmdline_lock); + preempt_enable(); } void tracing_record_cmdline(struct task_struct *tsk)