From: Eran Ben Elisha eranbe@nvidia.com
commit 410bd754cd73c4a2ac3856d9a03d7b08f9c906bf upstream.
It is possible that new command entry index allocation will temporarily fail. The new command holds the semaphore, so it means that a free entry should be ready soon. Add one second retry mechanism before returning an error.
Patch "net/mlx5: Avoid possible free of command entry while timeout comp handler" increase the possibility to bump into this temporarily failure as it delays the entry index release for non-callback commands.
Fixes: e126ba97dba9 ("mlx5: Add driver for Mellanox Connect-IB adapters") Signed-off-by: Eran Ben Elisha eranbe@nvidia.com Reviewed-by: Moshe Shemesh moshe@nvidia.com Signed-off-by: Saeed Mahameed saeedm@nvidia.com Cc: Timo Rothenpieler timo@rothenpieler.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/net/ethernet/mellanox/mlx5/core/cmd.c | 21 ++++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-)
--- a/drivers/net/ethernet/mellanox/mlx5/core/cmd.c +++ b/drivers/net/ethernet/mellanox/mlx5/core/cmd.c @@ -883,6 +883,25 @@ static bool opcode_allowed(struct mlx5_c return cmd->allowed_opcode == opcode; }
+static int cmd_alloc_index_retry(struct mlx5_cmd *cmd) +{ + unsigned long alloc_end = jiffies + msecs_to_jiffies(1000); + int idx; + +retry: + idx = cmd_alloc_index(cmd); + if (idx < 0 && time_before(jiffies, alloc_end)) { + /* Index allocation can fail on heavy load of commands. This is a temporary + * situation as the current command already holds the semaphore, meaning that + * another command completion is being handled and it is expected to release + * the entry index soon. + */ + cpu_relax(); + goto retry; + } + return idx; +} + static void cmd_work_handler(struct work_struct *work) { struct mlx5_cmd_work_ent *ent = container_of(work, struct mlx5_cmd_work_ent, work); @@ -900,7 +919,7 @@ static void cmd_work_handler(struct work sem = ent->page_queue ? &cmd->pages_sem : &cmd->sem; down(sem); if (!ent->page_queue) { - alloc_ret = cmd_alloc_index(cmd); + alloc_ret = cmd_alloc_index_retry(cmd); if (alloc_ret < 0) { mlx5_core_err(dev, "failed to allocate command entry\n"); if (ent->callback) {