From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: linux-kernel@vger.kernel.org
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Will Deacon <will@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
"Paul E . McKenney" <paulmck@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Matthew Wilcox <willy@infradead.org>,
Mike Galbraith <umgwanakikbuti@gmail.com>,
Minchan Kim <minchan@kernel.org>, Nitin Gupta <ngupta@vflare.org>,
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Subject: [PATCH v3 7/7] zram: Use local lock to protect per-CPU data
Date: Wed, 27 May 2020 22:11:19 +0200 [thread overview]
Message-ID: <20200527201119.1692513-8-bigeasy@linutronix.de> (raw)
In-Reply-To: <20200527201119.1692513-1-bigeasy@linutronix.de>
From: Mike Galbraith <umgwanakikbuti@gmail.com>
The zcomp driver uses per-CPU compression. The per-CPU data pointer is
acquired with get_cpu_ptr() which implicitly disables preemption.
It allocates memory inside the preempt disabled region which conflicts
with the PREEMPT_RT semantics.
Replace the implicit preemption control with an explicit local lock.
This allows RT kernels to substitute it with a real per CPU lock, which
serializes the access but keeps the code section preemptible. On non RT
kernels this maps to preempt_disable() as before, i.e. no functional
change.
[bigeasy: Use local_lock(), description, drop reordering]
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
drivers/block/zram/zcomp.c | 7 +++++--
drivers/block/zram/zcomp.h | 3 +++
2 files changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c
index 912e3e63d8a09..5ee8e3fae5516 100644
--- a/drivers/block/zram/zcomp.c
+++ b/drivers/block/zram/zcomp.c
@@ -110,12 +110,13 @@ ssize_t zcomp_available_show(const char *comp, char *buf)
struct zcomp_strm *zcomp_stream_get(struct zcomp *comp)
{
- return get_cpu_ptr(comp->stream);
+ local_lock(&comp->stream->lock);
+ return this_cpu_ptr(comp->stream);
}
void zcomp_stream_put(struct zcomp *comp)
{
- put_cpu_ptr(comp->stream);
+ local_unlock(&comp->stream->lock);
}
int zcomp_compress(struct zcomp_strm *zstrm,
@@ -159,6 +160,8 @@ int zcomp_cpu_up_prepare(unsigned int cpu, struct hlist_node *node)
int ret;
zstrm = per_cpu_ptr(comp->stream, cpu);
+ local_lock_init(&zstrm->lock);
+
ret = zcomp_strm_init(zstrm, comp);
if (ret)
pr_err("Can't allocate a compression stream\n");
diff --git a/drivers/block/zram/zcomp.h b/drivers/block/zram/zcomp.h
index 72c2ee4d843ed..40f6420f4b2e9 100644
--- a/drivers/block/zram/zcomp.h
+++ b/drivers/block/zram/zcomp.h
@@ -5,8 +5,11 @@
#ifndef _ZCOMP_H_
#define _ZCOMP_H_
+#include <linux/local_lock.h>
struct zcomp_strm {
+ /* The members ->buffer and ->tfm are protected by ->lock. */
+ local_lock_t lock;
/* compression/decompression buffer */
void *buffer;
struct crypto_comp *tfm;
--
2.27.0.rc0
next prev parent reply other threads:[~2020-05-27 20:11 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-27 20:11 [PATCH v3 0/7] Introduce local_lock() Sebastian Andrzej Siewior
2020-05-27 20:11 ` [PATCH v3 1/7] locking: " Sebastian Andrzej Siewior
2020-06-01 9:52 ` [tip: locking/core] " tip-bot2 for Thomas Gleixner
2020-05-27 20:11 ` [PATCH v3 2/7] radix-tree: Use local_lock for protection Sebastian Andrzej Siewior
2020-06-01 9:52 ` [tip: locking/core] " tip-bot2 for Sebastian Andrzej Siewior
2020-05-27 20:11 ` [PATCH v3 3/7] mm/swap: " Sebastian Andrzej Siewior
2020-06-01 9:52 ` [tip: locking/core] " tip-bot2 for Ingo Molnar
2020-05-27 20:11 ` [PATCH v3 4/7] squashfs: make use of local lock in multi_cpu decompressor Sebastian Andrzej Siewior
2020-06-01 9:52 ` [tip: locking/core] squashfs: Make " tip-bot2 for Julia Cartwright
2020-05-27 20:11 ` [PATCH v3 5/7] connector/cn_proc: Protect send_msg() with a local lock Sebastian Andrzej Siewior
2020-06-01 9:52 ` [tip: locking/core] " tip-bot2 for Mike Galbraith
2020-05-27 20:11 ` [PATCH v3 6/7] zram: Allocate struct zcomp_strm as per-CPU memory Sebastian Andrzej Siewior
2020-05-29 20:51 ` Minchan Kim
2020-06-01 9:52 ` [tip: locking/core] " tip-bot2 for Sebastian Andrzej Siewior
2020-05-27 20:11 ` Sebastian Andrzej Siewior [this message]
2020-05-29 20:57 ` [PATCH v3 7/7] zram: Use local lock to protect per-CPU data Minchan Kim
2020-06-01 9:52 ` [tip: locking/core] " tip-bot2 for Mike Galbraith
2020-10-19 1:52 ` [PATCH v3 7/7] " Yu Zhao
2020-10-19 2:33 ` Hugh Dickins
2020-10-19 2:46 ` Mike Galbraith
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