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gpu: nvgpu: Fix PMU destroy sequence

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A call to exit the PMU state machine/kthread must
be prioritized over any other state change.
It was possible to set the state as PMU_STATE_EXIT,
signal the kthread and overwrite the state before
the kthread has had the chance to exit its loop.
This may lead to a "lost" signal, resulting in
indefinite wait during the destroy sequence.

Faulting sequence:
1. pmu_state = PMU_STATE_EXIT in nvgpu_pmu_destroy()
2. cond_signal()
3. pmu_state = PMU_STATE_LOADING_PG_BUF
4. PMU kthread wakes up
5. PMU kthread processes PMU_STATE_LOADING_PG_BUF
6. PMU kthread sleeps
7. nvgpu_pmu_destroy() waits indefinitely

This patch adds a sticky flag to indicate PMU_STATE_EXIT,
irrespective of any subsequent changes to pmu_state.

The PMU PG init kthread may wait on a call to
NVGPU_COND_WAIT_INTERRUPTIBLE, which requires a
corresponding call to nvgpu_cond_signal_interruptible()
as the core kernel code requires this task mask to
wake-up an interruptible task.

Bug 2658750
Bug 200532122

Change-Id: I61beae80673486f83bf60c703a8af88b066a1c36
Signed-off-by: Divya Singhatwaria <dsinghatwari@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/2181926
Reviewed-by: svc-mobile-coverity <svc-mobile-coverity@nvidia.com>
Reviewed-by: svc-mobile-misra <svc-mobile-misra@nvidia.com>
Reviewed-by: Mahantesh Kumbar <mkumbar@nvidia.com>
GVS: Gerrit_Virtual_Submit
Reviewed-by: Deepak Nibade <dnibade@nvidia.com>
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>
This commit is contained in:
Divya Singhatwaria
2019-08-23 15:45:48 +05:30
committed by mobile promotions
parent 17b06bcddd
commit dc366ea4b4
3 changed files with 8 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
drivers/gpu/nvgpu/common/pmu/fw/fw.c
View File

@@ -65,6 +65,10 @@ void nvgpu_pmu_fw_state_change(struct gk20a *g, struct nvgpu_pmu *pmu,
nvgpu_smp_wmb();
pmu->fw->state = pmu_state;
/* Set a sticky flag to indicate PMU state exit */
if (pmu_state == PMU_FW_STATE_EXIT) {
pmu->pg->pg_init.state_destroy = true;
}
if (post_change_event) {
if (g->can_elpg) {
pmu->pg->pg_init.state_change = true;

4
drivers/gpu/nvgpu/common/pmu/pg/pmu_pg.c
View File

@@ -798,6 +798,8 @@ static void pmu_pg_kill_task(struct gk20a *g, struct nvgpu_pmu *pmu,
nvgpu_udelay(2);
} while (nvgpu_timeout_expired_msg(&timeout,
"timeout - waiting PMU state machine thread stop") == 0);
/* Reset the flag for next time */
pmu->pg->pg_init.state_destroy = false;
} else {
nvgpu_thread_join(&pg->pg_init.state_task);
}
@@ -821,7 +823,7 @@ static int pmu_pg_task(void *arg)
pmu->pg->pg_init.state_change = false;
pmu_state = nvgpu_pmu_get_fw_state(g, pmu);
if (pmu_state == PMU_FW_STATE_EXIT) {
if (pmu->pg->pg_init.state_destroy) {
nvgpu_pmu_dbg(g, "pmu state exit");
break;
}

1
drivers/gpu/nvgpu/include/nvgpu/pmu/pmu_pg.h
View File

@@ -61,6 +61,7 @@ struct pmu_pg_stats_data;
struct nvgpu_pg_init {
bool state_change;
bool state_destroy;
struct nvgpu_cond wq;
struct nvgpu_thread state_task;
};