linux-kernel - [tip:perfcounters/core] perf_counter: fix the output lock

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 5 May 2009 18:34:34 GMT
From:	tip-bot for Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, paulus@...ba.org, hpa@...or.com,
	mingo@...hat.com, a.p.zijlstra@...llo.nl, tglx@...utronix.de,
	cjashfor@...ux.vnet.ibm.com, mingo@...e.hu
Subject: [tip:perfcounters/core] perf_counter: fix the output lock

Commit-ID:  22c1558e51c210787c6cf75d8905246fc91ec030
Gitweb:     http://git.kernel.org/tip/22c1558e51c210787c6cf75d8905246fc91ec030
Author:     Peter Zijlstra <a.p.zijlstra@...llo.nl>
AuthorDate: Tue, 5 May 2009 17:50:25 +0200
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Tue, 5 May 2009 20:18:32 +0200

perf_counter: fix the output lock

Use -1 instead of 0 as unlocked, since 0 is a valid cpu number.

( This is not an issue right now but will be once we allow multiple
  counters to output to the same mmap area. )

[ Impact: prepare code for multi-counter profile output ]

Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Corey Ashford <cjashfor@...ux.vnet.ibm.com>
LKML-Reference: <20090505155437.232686598@...llo.nl>
Signed-off-by: Ingo Molnar <mingo@...e.hu>


---
 kernel/perf_counter.c |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index 2d13427..c881afe 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -1409,6 +1409,7 @@ static int perf_mmap_data_alloc(struct perf_counter *counter, int nr_pages)
 	}
 
 	data->nr_pages = nr_pages;
+	atomic_set(&data->lock, -1);
 
 	rcu_assign_pointer(counter->data, data);
 
@@ -1755,7 +1756,7 @@ static void perf_output_lock(struct perf_output_handle *handle)
 	if (in_nmi() && atomic_read(&data->lock) == cpu)
 		return;
 
-	while (atomic_cmpxchg(&data->lock, 0, cpu) != 0)
+	while (atomic_cmpxchg(&data->lock, -1, cpu) != -1)
 		cpu_relax();
 
 	handle->locked = 1;
@@ -1784,7 +1785,7 @@ again:
 	 * NMI can happen here, which means we can miss a done_head update.
 	 */
 
-	cpu = atomic_xchg(&data->lock, 0);
+	cpu = atomic_xchg(&data->lock, -1);
 	WARN_ON_ONCE(cpu != smp_processor_id());
 
 	/*
@@ -1794,7 +1795,7 @@ again:
 		/*
 		 * Since we had it locked, we can lock it again.
 		 */
-		while (atomic_cmpxchg(&data->lock, 0, cpu) != 0)
+		while (atomic_cmpxchg(&data->lock, -1, cpu) != -1)
 			cpu_relax();
 
 		goto again;
--
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/