Re: [PATCH v1 2/3] misc: fastrpc: wake poll-mode waiters on SSR

[Ekansh Gupta]

On 07-10-2026 14:14, Jianping Li wrote:
> fastrpc_notify_users() sets ctx->retval to -EPIPE and completes
> ctx->work for every pending and interrupted context, which is enough to
> release a thread blocked in fastrpc_wait_for_response().
> 
> A thread using polling mode does not wait on that completion. It spins
> in poll_for_remote_response(), whose exit condition is:
> 
>   (val == FASTRPC_POLL_RESPONSE) || ctx->is_work_done
> 
> Since the DSP is already down, it will never write FASTRPC_POLL_RESPONSE
> into the poll address, and is_work_done is left untouched by
> fastrpc_notify_users(). The thread therefore keeps spinning until
> FASTRPC_POLL_MAX_TIMEOUT_US expires instead of bailing out immediately.
> 
> Worse, the poll address lives inside ctx->buf, so a polling thread that
> has not been told to stop is still reading a buffer that the SSR
> teardown path is about to reclaim.
> 
> Set is_work_done along with retval so polling waiters observe the
> termination on their next iteration, exactly like completion waiters do.
> 
> Signed-off-by: Jianping Li <jianping.li@xxxxxxxxxxxxxxxx>

This looks to be a bug fix, can you please add Fixes: tag?

> ---
>  drivers/misc/fastrpc.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
> index 05b2e7e4ad3b..c54c450cb571 100644
> --- a/drivers/misc/fastrpc.c
> +++ b/drivers/misc/fastrpc.c
> @@ -2663,6 +2663,7 @@ static void fastrpc_notify_users(struct fastrpc_user *user)
>  	spin_lock(&user->lock);
>  	list_for_each_entry(ctx, &user->pending, node) {
>  		ctx->retval = -EPIPE;
> +		ctx->is_work_done = true;
>  		complete(&ctx->work);
>  	}
>  	spin_unlock(&user->lock);