Messages in this thread | | | Date | Fri, 18 Sep 2009 06:31:44 +0200 | From | Frederic Weisbecker <> | Subject | Re: [PATCH 2/2] tracing: Allocate the ftrace event profile buffer dynamically |
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On Fri, Sep 18, 2009 at 06:24:14AM +0200, Frederic Weisbecker wrote: > static void prof_syscall_enter(struct pt_regs *regs, long id) > { > - struct syscall_trace_enter *rec; > struct syscall_metadata *sys_data; > + struct syscall_trace_enter *rec; > + char *raw_data; > int syscall_nr; > int size; > + int cpu; > > syscall_nr = syscall_get_nr(current, regs); > if (!test_bit(syscall_nr, enabled_prof_enter_syscalls)) > @@ -402,20 +404,39 @@ static void prof_syscall_enter(struct pt_regs *regs, long id) > size = ALIGN(size + sizeof(u32), sizeof(u64)); > size -= sizeof(u32); > > - do { > - char raw_data[size]; > + if (WARN_ONCE(size > FTRACE_MAX_PROFILE_SIZE, > + "profile buffer not large enough")) > + return; > + > + /* > + * We are not in nmi. Also we can't be preempted by a sysenter event > + * from interrupt, so we can safely take this buffer without > + * masking interrupts. But we still need rcu_read_lock to protect > + * against concurrent buffer release. > + */ > + rcu_read_lock();
Oh...now that we use a global buffer, the buffer is not safe anymore against interrupts or NMIs.
Looks like I will need a third iteration.
Sorry for the noise...
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