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Date: Wed, 13 Jan 2010 21:56:07 -0500 From: Steven Rostedt <rostedt@...dmis.org> To: Christoph Lameter <cl@...ux-foundation.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>, Tejun Heo <tj@...nel.org>, linux-kernel@...r.kernel.org Subject: Re: [RFC local_t removal V1 2/4] Replace local_t use in trace subsystem Please Cc me on changes to the ring buffer. On Tue, 2010-01-05 at 16:04 -0600, Christoph Lameter wrote: > plain text document attachment (remove_local_t_ringbuffer_convert) > Replace the local_t use with longs in the trace subsystem. The longs can then be > updated with the required level of concurrency protection through cmpxchg_local() > and add_local(). > > Signed-off-by: Christoph Lameter <cl@...ux-foundation.org> > > @@ -1741,7 +1741,7 @@ rb_reset_tail(struct ring_buffer_per_cpu > * must fill the old tail_page with padding. > */ > if (tail >= BUF_PAGE_SIZE) { > - local_sub(length, &tail_page->write); > + add_local(&tail_page->write, -length); Can't you have a helper function or macro that does: #define sub_local(local, val) add_local(local, -(val)) > return; > } > > static struct ring_buffer_event * > @@ -1801,7 +1801,7 @@ rb_move_tail(struct ring_buffer_per_cpu > * about it. > */ > if (unlikely(next_page == commit_page)) { > - local_inc(&cpu_buffer->commit_overrun); > + add_local(&cpu_buffer->commit_overrun, 1); As well as a: #define inc_local(local) add_local(local, 1) > goto out_reset; > } > > again: > - commits = local_read(&cpu_buffer->commits); > + commits = cpu_buffer->commits; > /* synchronize with interrupts */ > barrier(); > - if (local_read(&cpu_buffer->committing) == 1) > + if (cpu_buffer->committing == 1) > rb_set_commit_to_write(cpu_buffer); > > - local_dec(&cpu_buffer->committing); > + add_local(&cpu_buffer->committing, -1); As well as a: #define dec_local(local) add_local(local, -1) > > /* synchronize with interrupts */ > barrier(); > @@ -2059,9 +2059,9 @@ static void rb_end_commit(struct ring_bu > * updating of the commit page and the clearing of the > * committing counter. > */ The reason I ask for the above is because it sticks out much better. The subtracting and inc/dec pairs I need to match. So I usually end up scanning a matching "dec" for a "inc", or a matching "sub" for an "add", but having "-1" to match "1" is not going to stand out, and I envision a lot of stupid bugs happening because of this. -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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