6.15-stable review patch. If anyone has any objections, please let me know.
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From: Breno Leitao leitao@debian.org
commit e14fd98c6d66cb76694b12c05768e4f9e8c95664 upstream.
Avoid invoking update_locked_rq() when the runqueue (rq) pointer is NULL in the SCX_CALL_OP and SCX_CALL_OP_RET macros.
Previously, calling update_locked_rq(NULL) with preemption enabled could trigger the following warning:
BUG: using __this_cpu_write() in preemptible [00000000]
This happens because __this_cpu_write() is unsafe to use in preemptible context.
rq is NULL when an ops invoked from an unlocked context. In such cases, we don't need to store any rq, since the value should already be NULL (unlocked). Ensure that update_locked_rq() is only called when rq is non-NULL, preventing calling __this_cpu_write() on preemptible context.
Suggested-by: Peter Zijlstra peterz@infradead.org Fixes: 18853ba782bef ("sched_ext: Track currently locked rq") Signed-off-by: Breno Leitao leitao@debian.org Acked-by: Andrea Righi arighi@nvidia.com Signed-off-by: Tejun Heo tj@kernel.org Cc: stable@vger.kernel.org # v6.15 Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/sched/ext.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-)
--- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -1149,7 +1149,8 @@ static inline struct rq *scx_locked_rq(v
#define SCX_CALL_OP(mask, op, rq, args...) \ do { \ - update_locked_rq(rq); \ + if (rq) \ + update_locked_rq(rq); \ if (mask) { \ scx_kf_allow(mask); \ scx_ops.op(args); \ @@ -1157,14 +1158,16 @@ do { \ } else { \ scx_ops.op(args); \ } \ - update_locked_rq(NULL); \ + if (rq) \ + update_locked_rq(NULL); \ } while (0)
#define SCX_CALL_OP_RET(mask, op, rq, args...) \ ({ \ __typeof__(scx_ops.op(args)) __ret; \ \ - update_locked_rq(rq); \ + if (rq) \ + update_locked_rq(rq); \ if (mask) { \ scx_kf_allow(mask); \ __ret = scx_ops.op(args); \ @@ -1172,7 +1175,8 @@ do { \ } else { \ __ret = scx_ops.op(args); \ } \ - update_locked_rq(NULL); \ + if (rq) \ + update_locked_rq(NULL); \ __ret; \ })