From: Mike Galbraith <[email protected]> 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 <[email protected]> Cc: Nitin Gupta <[email protected]> Cc: Sergey Senozhatsky <[email protected]> Signed-off-by: Mike Galbraith <[email protected]> Signed-off-by: Sebastian Andrzej Siewior <[email protected]> --- drivers/block/zram/zcomp.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c index 1a8564a79d8dc..32854d460b299 100644 --- a/drivers/block/zram/zcomp.c +++ b/drivers/block/zram/zcomp.c @@ -11,6 +11,7 @@ #include <linux/sched.h> #include <linux/cpu.h> #include <linux/crypto.h> +#include <linux/locallock.h> #include "zcomp.h" @@ -111,14 +112,17 @@ ssize_t zcomp_available_show(const char *comp, char *buf) return sz; } +static DEFINE_LOCAL_LOCK(zcomp_lock); + struct zcomp_strm *zcomp_stream_get(struct zcomp *comp) { - return *get_cpu_ptr(comp->stream); + local_lock(zcomp_lock); + return *this_cpu_ptr(comp->stream); } void zcomp_stream_put(struct zcomp *comp) { - put_cpu_ptr(comp->stream); + local_unlock(zcomp_lock); } int zcomp_compress(struct zcomp_strm *zstrm, -- 2.26.2
