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-rw-r--r--drivers/misc/cxl/api.c2
-rw-r--r--drivers/misc/cxl/context.c6
-rw-r--r--drivers/misc/cxl/cxl.h3
-rw-r--r--drivers/misc/cxl/fault.c129
-rw-r--r--drivers/misc/cxl/file.c6
5 files changed, 109 insertions, 37 deletions
diff --git a/drivers/misc/cxl/api.c b/drivers/misc/cxl/api.c
index a6543aefa299..ea3eeb7011e1 100644
--- a/drivers/misc/cxl/api.c
+++ b/drivers/misc/cxl/api.c
@@ -172,7 +172,7 @@ int cxl_start_context(struct cxl_context *ctx, u64 wed,
if (task) {
ctx->pid = get_task_pid(task, PIDTYPE_PID);
- get_pid(ctx->pid);
+ ctx->glpid = get_task_pid(task->group_leader, PIDTYPE_PID);
kernel = false;
}
diff --git a/drivers/misc/cxl/context.c b/drivers/misc/cxl/context.c
index 6dde7a9d6a7e..262b88eac414 100644
--- a/drivers/misc/cxl/context.c
+++ b/drivers/misc/cxl/context.c
@@ -42,7 +42,7 @@ int cxl_context_init(struct cxl_context *ctx, struct cxl_afu *afu, bool master,
spin_lock_init(&ctx->sste_lock);
ctx->afu = afu;
ctx->master = master;
- ctx->pid = NULL; /* Set in start work ioctl */
+ ctx->pid = ctx->glpid = NULL; /* Set in start work ioctl */
mutex_init(&ctx->mapping_lock);
ctx->mapping = mapping;
@@ -217,7 +217,11 @@ int __detach_context(struct cxl_context *ctx)
WARN_ON(cxl_detach_process(ctx) &&
cxl_adapter_link_ok(ctx->afu->adapter));
flush_work(&ctx->fault_work); /* Only needed for dedicated process */
+
+ /* release the reference to the group leader and mm handling pid */
put_pid(ctx->pid);
+ put_pid(ctx->glpid);
+
cxl_ctx_put();
return 0;
}
diff --git a/drivers/misc/cxl/cxl.h b/drivers/misc/cxl/cxl.h
index 25ae57fa79b0..a521bc72cec2 100644
--- a/drivers/misc/cxl/cxl.h
+++ b/drivers/misc/cxl/cxl.h
@@ -445,6 +445,9 @@ struct cxl_context {
unsigned int sst_size, sst_lru;
wait_queue_head_t wq;
+ /* pid of the group leader associated with the pid */
+ struct pid *glpid;
+ /* use mm context associated with this pid for ds faults */
struct pid *pid;
spinlock_t lock; /* Protects pending_irq_mask, pending_fault and fault_addr */
/* Only used in PR mode */
diff --git a/drivers/misc/cxl/fault.c b/drivers/misc/cxl/fault.c
index 25a5418c55cb..81c3f75b7330 100644
--- a/drivers/misc/cxl/fault.c
+++ b/drivers/misc/cxl/fault.c
@@ -166,13 +166,92 @@ static void cxl_handle_page_fault(struct cxl_context *ctx,
cxl_ack_irq(ctx, CXL_PSL_TFC_An_R, 0);
}
+/*
+ * Returns the mm_struct corresponding to the context ctx via ctx->pid
+ * In case the task has exited we use the task group leader accessible
+ * via ctx->glpid to find the next task in the thread group that has a
+ * valid mm_struct associated with it. If a task with valid mm_struct
+ * is found the ctx->pid is updated to use the task struct for subsequent
+ * translations. In case no valid mm_struct is found in the task group to
+ * service the fault a NULL is returned.
+ */
+static struct mm_struct *get_mem_context(struct cxl_context *ctx)
+{
+ struct task_struct *task = NULL;
+ struct mm_struct *mm = NULL;
+ struct pid *old_pid = ctx->pid;
+
+ if (old_pid == NULL) {
+ pr_warn("%s: Invalid context for pe=%d\n",
+ __func__, ctx->pe);
+ return NULL;
+ }
+
+ task = get_pid_task(old_pid, PIDTYPE_PID);
+
+ /*
+ * pid_alive may look racy but this saves us from costly
+ * get_task_mm when the task is a zombie. In worst case
+ * we may think a task is alive, which is about to die
+ * but get_task_mm will return NULL.
+ */
+ if (task != NULL && pid_alive(task))
+ mm = get_task_mm(task);
+
+ /* release the task struct that was taken earlier */
+ if (task)
+ put_task_struct(task);
+ else
+ pr_devel("%s: Context owning pid=%i for pe=%i dead\n",
+ __func__, pid_nr(old_pid), ctx->pe);
+
+ /*
+ * If we couldn't find the mm context then use the group
+ * leader to iterate over the task group and find a task
+ * that gives us mm_struct.
+ */
+ if (unlikely(mm == NULL && ctx->glpid != NULL)) {
+
+ rcu_read_lock();
+ task = pid_task(ctx->glpid, PIDTYPE_PID);
+ if (task)
+ do {
+ mm = get_task_mm(task);
+ if (mm) {
+ ctx->pid = get_task_pid(task,
+ PIDTYPE_PID);
+ break;
+ }
+ task = next_thread(task);
+ } while (task && !thread_group_leader(task));
+ rcu_read_unlock();
+
+ /* check if we switched pid */
+ if (ctx->pid != old_pid) {
+ if (mm)
+ pr_devel("%s:pe=%i switch pid %i->%i\n",
+ __func__, ctx->pe, pid_nr(old_pid),
+ pid_nr(ctx->pid));
+ else
+ pr_devel("%s:Cannot find mm for pid=%i\n",
+ __func__, pid_nr(old_pid));
+
+ /* drop the reference to older pid */
+ put_pid(old_pid);
+ }
+ }
+
+ return mm;
+}
+
+
+
void cxl_handle_fault(struct work_struct *fault_work)
{
struct cxl_context *ctx =
container_of(fault_work, struct cxl_context, fault_work);
u64 dsisr = ctx->dsisr;
u64 dar = ctx->dar;
- struct task_struct *task = NULL;
struct mm_struct *mm = NULL;
if (cxl_p2n_read(ctx->afu, CXL_PSL_DSISR_An) != dsisr ||
@@ -195,17 +274,17 @@ void cxl_handle_fault(struct work_struct *fault_work)
"DSISR: %#llx DAR: %#llx\n", ctx->pe, dsisr, dar);
if (!ctx->kernel) {
- if (!(task = get_pid_task(ctx->pid, PIDTYPE_PID))) {
- pr_devel("cxl_handle_fault unable to get task %i\n",
- pid_nr(ctx->pid));
+
+ mm = get_mem_context(ctx);
+ /* indicates all the thread in task group have exited */
+ if (mm == NULL) {
+ pr_devel("%s: unable to get mm for pe=%d pid=%i\n",
+ __func__, ctx->pe, pid_nr(ctx->pid));
cxl_ack_ae(ctx);
return;
- }
- if (!(mm = get_task_mm(task))) {
- pr_devel("cxl_handle_fault unable to get mm %i\n",
- pid_nr(ctx->pid));
- cxl_ack_ae(ctx);
- goto out;
+ } else {
+ pr_devel("Handling page fault for pe=%d pid=%i\n",
+ ctx->pe, pid_nr(ctx->pid));
}
}
@@ -218,33 +297,22 @@ void cxl_handle_fault(struct work_struct *fault_work)
if (mm)
mmput(mm);
-out:
- if (task)
- put_task_struct(task);
}
static void cxl_prefault_one(struct cxl_context *ctx, u64 ea)
{
- int rc;
- struct task_struct *task;
struct mm_struct *mm;
- if (!(task = get_pid_task(ctx->pid, PIDTYPE_PID))) {
- pr_devel("cxl_prefault_one unable to get task %i\n",
- pid_nr(ctx->pid));
- return;
- }
- if (!(mm = get_task_mm(task))) {
+ mm = get_mem_context(ctx);
+ if (mm == NULL) {
pr_devel("cxl_prefault_one unable to get mm %i\n",
pid_nr(ctx->pid));
- put_task_struct(task);
return;
}
- rc = cxl_fault_segment(ctx, mm, ea);
+ cxl_fault_segment(ctx, mm, ea);
mmput(mm);
- put_task_struct(task);
}
static u64 next_segment(u64 ea, u64 vsid)
@@ -263,18 +331,13 @@ static void cxl_prefault_vma(struct cxl_context *ctx)
struct copro_slb slb;
struct vm_area_struct *vma;
int rc;
- struct task_struct *task;
struct mm_struct *mm;
- if (!(task = get_pid_task(ctx->pid, PIDTYPE_PID))) {
- pr_devel("cxl_prefault_vma unable to get task %i\n",
- pid_nr(ctx->pid));
- return;
- }
- if (!(mm = get_task_mm(task))) {
+ mm = get_mem_context(ctx);
+ if (mm == NULL) {
pr_devel("cxl_prefault_vm unable to get mm %i\n",
pid_nr(ctx->pid));
- goto out1;
+ return;
}
down_read(&mm->mmap_sem);
@@ -295,8 +358,6 @@ static void cxl_prefault_vma(struct cxl_context *ctx)
up_read(&mm->mmap_sem);
mmput(mm);
-out1:
- put_task_struct(task);
}
void cxl_prefault(struct cxl_context *ctx, u64 wed)
diff --git a/drivers/misc/cxl/file.c b/drivers/misc/cxl/file.c
index 5cc14599837d..783337d22f36 100644
--- a/drivers/misc/cxl/file.c
+++ b/drivers/misc/cxl/file.c
@@ -201,8 +201,12 @@ static long afu_ioctl_start_work(struct cxl_context *ctx,
* where a process (master, some daemon, etc) has opened the chardev on
* behalf of another process, so the AFU's mm gets bound to the process
* that performs this ioctl and not the process that opened the file.
+ * Also we grab the PID of the group leader so that if the task that
+ * has performed the attach operation exits the mm context of the
+ * process is still accessible.
*/
- ctx->pid = get_pid(get_task_pid(current, PIDTYPE_PID));
+ ctx->pid = get_task_pid(current, PIDTYPE_PID);
+ ctx->glpid = get_task_pid(current->group_leader, PIDTYPE_PID);
trace_cxl_attach(ctx, work.work_element_descriptor, work.num_interrupts, amr);
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-07 08:54:17 +0000