The following commit has been merged into the locking/core branch of tip: Commit-ID: 19f545b6e07f753c4dc639c2f0ab52345733b6a8 Gitweb: https://git.kernel.org/tip/19f545b6e07f753c4dc639c2f0ab52345733b6a8 Author: Mike Galbraith <umgwanakikb...@gmail.com> AuthorDate: Wed, 27 May 2020 22:11:19 +02:00 Committer: Ingo Molnar <mi...@kernel.org> CommitterDate: Thu, 28 May 2020 10:31:10 +02:00
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 <umgwanakikb...@gmail.com> Signed-off-by: Sebastian Andrzej Siewior <bige...@linutronix.de> Signed-off-by: Ingo Molnar <mi...@kernel.org> Acked-by: Peter Zijlstra <pet...@infradead.org> Link: https://lore.kernel.org/r/20200527201119.1692513-8-bige...@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 912e3e6..5ee8e3f 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 72c2ee4..40f6420 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;
