fastrpc invokes work by sending an RPC message to the DSP and blocking
in wait_for_completion_interruptible() until the DSP responds. If a
signal arrives during this wait, the syscall returns -ERESTARTSYS and
the invoke context which holds the in-flight DMA buffers and
completion state is left stranded in fl->pending.
On the next syscall attempt (either auto-restarted by the kernel via
SA_RESTART or manually retried by user-space after EINTR), a fresh
context is allocated and the RPC message is re-sent to the DSP. This
has two consequences:
- The original context leaks in fl->pending until the file is closed.
- The DSP receives a duplicate invocation. If the DSP was mid-way
through processing the first request and had issued a reverse RPC
call back to the host, the retry sends a new forward request
instead of the expected reverse-RPC response. The DSP thread
waiting for that response is never woken, causing a hang.
Fix this by saving the interrupted context to a new fl->interrupted
list on -ERESTARTSYS. When the same thread retries the invoke with a
matching sc, restore the context and jump directly to the wait,
skipping context allocation and message re-send.
Three additional bugs are also fixed:
1. fastrpc_context_save_interrupted() did not drop the extra kref that
fastrpc_invoke_send() took, so the worker's put only reached 1 and
the context was never freed. Drop the reference in save_interrupted()
so the worker's put reaches 0 and triggers context_free.
2. The bail path skipped context cleanup on -ETIMEDOUT, leaking the
context. Remove the -ETIMEDOUT exception so timed-out contexts are
freed like any other error path.
3. fastrpc_context_free() did not remove the context from fl->interrupted
before freeing it. A context freed via a racing channel removal left
a dangling node in the list. Add list_del_init() guarded by fl->lock
before releasing resources.
Also drain fl->interrupted on process exit, complete any sleeping
contexts with -EPIPE and schedule put_wq to drop the worker ref when
the rpmsg channel is removed, and add dev_warn() on TIMEOUT and
ERESTARTSYS to aid post-mortem debugging.
Remove the obsolete invoke_interrupted_mmaps mechanism from
fastrpc_channel_ctx; context resources are now kept alive through the
context refcount rather than by migrating mmaps to a channel-level list.
Fixes: 387f625585d1 ("misc: fastrpc: handle interrupted contexts")
Cc: [email protected]
Co-developed-by: Srinivas Kandagatla <[email protected]>
Signed-off-by: Srinivas Kandagatla <[email protected]>
Signed-off-by: Anandu Krishnan E <[email protected]>
---
This patch fixes a context leak and DSP hang that occur when a
fastrpc invoke syscall is interrupted by a signal, along with three
follow-on bugs found during review.
Changes in v2:
- Fix kref imbalance: fastrpc_context_save_interrupted() now drops the
extra reference taken by fastrpc_invoke_send(), so the worker's put
correctly reaches 0 and triggers context_free.
- Fix -ETIMEDOUT context leak: remove the ETIMEDOUT exception from the
bail path so timed-out kernel invocations go through the same
list_del_init + context_put cleanup as all other error paths.
- Fix dangling node: fastrpc_context_free() now calls list_del_init()
under fl->lock before releasing resources, preventing a dangling node
in fl->interrupted if a racing channel removal fires put_wq.
- fastrpc_notify_users() now calls schedule_work(&ctx->put_work) for
interrupted contexts to drop the worker ref on channel removal.
- Add dev_warn() on TIMEOUT and ERESTARTSYS for post-mortem debugging.
- Use list_del_init() instead of list_del() in the bail path.
Link to v1:
https://lore.kernel.org/all/[email protected]/
---
drivers/misc/fastrpc.c | 101 +++++++++++++++++++++++++++++++++++++++----------
1 file changed, 82 insertions(+), 19 deletions(-)
diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
index f3a49384586d..c0859a501617 100644
--- a/drivers/misc/fastrpc.c
+++ b/drivers/misc/fastrpc.c
@@ -280,7 +280,6 @@ struct fastrpc_channel_ctx {
struct fastrpc_device *secure_fdevice;
struct fastrpc_device *fdevice;
struct fastrpc_buf *remote_heap;
- struct list_head invoke_interrupted_mmaps;
bool secure;
bool unsigned_support;
u64 dma_mask;
@@ -297,6 +296,7 @@ struct fastrpc_user {
struct list_head user;
struct list_head maps;
struct list_head pending;
+ struct list_head interrupted;
struct list_head mmaps;
struct fastrpc_channel_ctx *cctx;
@@ -522,6 +522,11 @@ static void fastrpc_user_free(struct kref *ref)
fastrpc_context_put(ctx);
}
+ list_for_each_entry_safe(ctx, n, &fl->interrupted, node) {
+ list_del(&ctx->node);
+ fastrpc_context_put(ctx);
+ }
+
list_for_each_entry_safe(map, m, &fl->maps, node)
fastrpc_map_put(map);
@@ -557,6 +562,12 @@ static void fastrpc_context_free(struct kref *ref)
cctx = ctx->cctx;
fl = ctx->fl;
+ /* Remove from fl->interrupted if present; no-op for normal paths. */
+ spin_lock(&fl->lock);
+ if (!list_empty(&ctx->node))
+ list_del_init(&ctx->node);
+ spin_unlock(&fl->lock);
+
for (i = 0; i < ctx->nbufs; i++)
fastrpc_map_put(ctx->maps[i]);
@@ -594,6 +605,42 @@ static void fastrpc_context_put_wq(struct work_struct
*work)
fastrpc_context_put(ctx);
}
+static void fastrpc_context_save_interrupted(struct fastrpc_invoke_ctx *ctx)
+{
+ spin_lock(&ctx->fl->lock);
+ list_del(&ctx->node);
+ list_add_tail(&ctx->node, &ctx->fl->interrupted);
+ spin_unlock(&ctx->fl->lock);
+ /*
+ * invoke_send bumped the kref to 2; the bail path skips the put
+ * for ERESTARTSYS. Drop it here so the worker's put reaches 0
+ * and triggers context_free.
+ */
+ fastrpc_context_put(ctx);
+}
+
+static struct fastrpc_invoke_ctx *fastrpc_context_restore_interrupted(
+ struct fastrpc_user *fl, u32 sc)
+{
+ struct fastrpc_invoke_ctx *ctx = NULL, *ictx, *n;
+
+ spin_lock(&fl->lock);
+ list_for_each_entry_safe(ictx, n, &fl->interrupted, node) {
+ if (ictx->pid != current->pid)
+ continue;
+ if (ictx->sc != sc || ictx->fl != fl) {
+ spin_unlock(&fl->lock);
+ return ERR_PTR(-EINVAL);
+ }
+ ctx = ictx;
+ list_del(&ctx->node);
+ list_add_tail(&ctx->node, &fl->pending);
+ break;
+ }
+ spin_unlock(&fl->lock);
+ return ctx;
+}
+
#define CMP(aa, bb) ((aa) == (bb) ? 0 : (aa) < (bb) ? -1 : 1)
static int olaps_cmp(const void *a, const void *b)
{
@@ -1243,8 +1290,6 @@ static int fastrpc_internal_invoke(struct fastrpc_user
*fl, u32 kernel,
struct fastrpc_invoke_args *args)
{
struct fastrpc_invoke_ctx *ctx = NULL;
- struct fastrpc_buf *buf, *b;
-
int err = 0;
if (!fl->sctx)
@@ -1258,6 +1303,14 @@ static int fastrpc_internal_invoke(struct fastrpc_user
*fl, u32 kernel,
return -EPERM;
}
+ if (!kernel) {
+ ctx = fastrpc_context_restore_interrupted(fl, sc);
+ if (IS_ERR(ctx))
+ return PTR_ERR(ctx);
+ if (ctx)
+ goto wait;
+ }
+
ctx = fastrpc_context_alloc(fl, kernel, sc, args);
if (IS_ERR(ctx))
return PTR_ERR(ctx);
@@ -1273,11 +1326,20 @@ static int fastrpc_internal_invoke(struct fastrpc_user
*fl, u32 kernel,
if (err)
goto bail;
+wait:
if (kernel) {
- if (!wait_for_completion_timeout(&ctx->work, 10 * HZ))
+ if (!wait_for_completion_timeout(&ctx->work, 10 * HZ)) {
err = -ETIMEDOUT;
+ dev_warn(fl->sctx->dev,
+ "fastrpc_invoke: TIMEOUT ctxid=0x%llx
handle=0x%x nscalars=%d\n",
+ ctx->ctxid, handle, ctx->nscalars);
+ }
} else {
err = wait_for_completion_interruptible(&ctx->work);
+ if (err == -ERESTARTSYS)
+ dev_warn(fl->sctx->dev,
+ "fastrpc_invoke: INTERRUPTED ctxid=0x%llx
handle=0x%x nscalars=%d\n",
+ ctx->ctxid, handle, ctx->nscalars);
}
if (err)
@@ -1296,21 +1358,15 @@ static int fastrpc_internal_invoke(struct fastrpc_user
*fl, u32 kernel,
goto bail;
bail:
- if (err != -ERESTARTSYS && err != -ETIMEDOUT) {
- /* We are done with this compute context */
+ if (ctx && err == -ERESTARTSYS) {
+ fastrpc_context_save_interrupted(ctx);
+ } else if (ctx) {
spin_lock(&fl->lock);
- list_del(&ctx->node);
+ list_del_init(&ctx->node);
spin_unlock(&fl->lock);
fastrpc_context_put(ctx);
}
- if (err == -ERESTARTSYS) {
- list_for_each_entry_safe(buf, b, &fl->mmaps, node) {
- list_del(&buf->node);
- list_add_tail(&buf->node,
&fl->cctx->invoke_interrupted_mmaps);
- }
- }
-
if (err)
dev_dbg(fl->sctx->dev, "Error: Invoke Failed %d\n", err);
@@ -1662,6 +1718,7 @@ static int fastrpc_device_open(struct inode *inode,
struct file *filp)
spin_lock_init(&fl->lock);
mutex_init(&fl->mutex);
INIT_LIST_HEAD(&fl->pending);
+ INIT_LIST_HEAD(&fl->interrupted);
INIT_LIST_HEAD(&fl->maps);
INIT_LIST_HEAD(&fl->mmaps);
INIT_LIST_HEAD(&fl->user);
@@ -2460,7 +2517,6 @@ static int fastrpc_rpmsg_probe(struct rpmsg_device *rpdev)
rdev->dma_mask = &data->dma_mask;
dma_set_mask_and_coherent(rdev, DMA_BIT_MASK(32));
INIT_LIST_HEAD(&data->users);
- INIT_LIST_HEAD(&data->invoke_interrupted_mmaps);
spin_lock_init(&data->lock);
idr_init(&data->ctx_idr);
data->domain_id = domain_id;
@@ -2493,13 +2549,23 @@ static void fastrpc_notify_users(struct fastrpc_user
*user)
ctx->retval = -EPIPE;
complete(&ctx->work);
}
+ /*
+ * Interrupted contexts hold two refs: one for the invoker and one
+ * for the async worker from fastrpc_invoke_send. Complete them so
+ * any blocked retry wakes, and schedule put_wq to drop the worker
+ * ref -- the invoker ref is released by fastrpc_user_free().
+ */
+ list_for_each_entry(ctx, &user->interrupted, node) {
+ ctx->retval = -EPIPE;
+ complete(&ctx->work);
+ schedule_work(&ctx->put_work);
+ }
spin_unlock(&user->lock);
}
static void fastrpc_rpmsg_remove(struct rpmsg_device *rpdev)
{
struct fastrpc_channel_ctx *cctx = dev_get_drvdata(&rpdev->dev);
- struct fastrpc_buf *buf, *b;
struct fastrpc_user *user;
unsigned long flags;
@@ -2516,9 +2582,6 @@ static void fastrpc_rpmsg_remove(struct rpmsg_device
*rpdev)
if (cctx->secure_fdevice)
misc_deregister(&cctx->secure_fdevice->miscdev);
- list_for_each_entry_safe(buf, b, &cctx->invoke_interrupted_mmaps, node)
- list_del(&buf->node);
-
if (cctx->remote_heap)
fastrpc_buf_free(cctx->remote_heap);
---
base-commit: dc59e4fea9d83f03bad6bddf3fa2e52491777482
change-id: 20260701-master-2ba6246f29d1
Best regards,
--
Anandu Krishnan E <[email protected]>
