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| author | Mike Galbraith <umgwanakikbuti@gmail.com> | 2020-05-27 22:11:19 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2020-05-28 10:31:10 +0200 |
| commit | 19f545b6e07f753c4dc639c2f0ab52345733b6a8 (patch) | |
| tree | 0280ea9f67d39a48f67716bf9fdf4d3554c93cf4 /drivers/block | |
| parent | ed19f19256be2949af1ab5634e62178d30a355c2 (diff) | |
| download | linux-19f545b6e07f753c4dc639c2f0ab52345733b6a8.tar.bz2 | |
zram: Use local lock to protect per-CPU data
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]
Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20200527201119.1692513-8-bigeasy@linutronix.de
Diffstat (limited to 'drivers/block')
| -rw-r--r-- | drivers/block/zram/zcomp.c | 7 | ||||
| -rw-r--r-- | 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 912e3e63d8a0..5ee8e3fae551 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 72c2ee4d843e..40f6420f4b2e 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; |