Re: [PATCH] drm/amdgpu: Fix blocking in RCU critical section(v2)
Hi Emil, Sorry for late reply. I was so busy last week and this week. Your logic looks correct, smarter and shorter. I feel relatively more difficult to understand the logic, with two "!" and one "||" in the same if statement. Thanks for the advice always. On 2017-07-20 02:29 PM, Emil Velikov wrote: Hi Alex, On 20 July 2017 at 03:46, Alex Xiewrote: --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c @@ -198,12 +198,18 @@ amdgpu_bo_list_get(struct amdgpu_fpriv *fpriv, int id) result = idr_find(>bo_list_handles, id); if (result) { - if (kref_get_unless_zero(>refcount)) + if (kref_get_unless_zero(>refcount)) { + rcu_read_unlock(); mutex_lock(>lock); - else + } + else { + rcu_read_unlock(); result = NULL; + } + } + else { + rcu_read_unlock(); } - rcu_read_unlock(); return result; A drive-by suggestion - feel free to ignore. The "return early" approach seems great IMHO. The code will be shorter, indentation - less, no {}/else to track plus overall it seems clearer. Namely: result = idr_find(>bo_list_handles, id); if (!result || !kref_get_unless_zero(>refcount)) { rcu_read_unlock(); return NULL; } rcu_read_unlock(); mutex_lock(>lock); return result; } HTH Emil ___ amd-gfx mailing list amd-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/amd-gfx
Re: [PATCH] drm/amdgpu: Fix blocking in RCU critical section(v2)
Hi Alex, On 20 July 2017 at 03:46, Alex Xiewrote: > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c > @@ -198,12 +198,18 @@ amdgpu_bo_list_get(struct amdgpu_fpriv *fpriv, int id) > result = idr_find(>bo_list_handles, id); > > if (result) { > - if (kref_get_unless_zero(>refcount)) > + if (kref_get_unless_zero(>refcount)) { > + rcu_read_unlock(); > mutex_lock(>lock); > - else > + } > + else { > + rcu_read_unlock(); > result = NULL; > + } > + } > + else { > + rcu_read_unlock(); > } > - rcu_read_unlock(); > > return result; A drive-by suggestion - feel free to ignore. The "return early" approach seems great IMHO. The code will be shorter, indentation - less, no {}/else to track plus overall it seems clearer. Namely: result = idr_find(>bo_list_handles, id); if (!result || !kref_get_unless_zero(>refcount)) { rcu_read_unlock(); return NULL; } rcu_read_unlock(); mutex_lock(>lock); return result; } HTH Emil ___ amd-gfx mailing list amd-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/amd-gfx
Re: [PATCH] drm/amdgpu: Fix blocking in RCU critical section(v2)
Yeah, with the coding style fixed Reviewed-by: Christian Königas well. Christian. Am 20.07.2017 um 05:01 schrieb zhoucm1: one small nit pick, with that fix, Reviewed-by: Chunming Zhou On 2017年07月20日 10:46, Alex Xie wrote: In RCU read-side critical sections, blocking or sleeping is prohibited. v2: Unlock RCU for the code path where result==NULL. (David Zhou) Update subject Tested-by and reported by: Dave Airlie [ 141.965723] = [ 141.965724] WARNING: suspicious RCU usage [ 141.965726] 4.12.0-rc7 #221 Not tainted [ 141.965727] - [ 141.965728] /home/airlied/devel/kernel/linux-2.6/include/linux/rcupdate.h:531 Illegal context switch in RCU read-side critical section! [ 141.965730] other info that might help us debug this: [ 141.965731] rcu_scheduler_active = 2, debug_locks = 0 [ 141.965732] 1 lock held by amdgpu_cs:0/1332: [ 141.965733] #0: (rcu_read_lock){..}, at: [] amdgpu_bo_list_get+0x0/0x109 [amdgpu] [ 141.965774] stack backtrace: [ 141.965776] CPU: 6 PID: 1332 Comm: amdgpu_cs:0 Not tainted 4.12.0-rc7 #221 [ 141.965777] Hardware name: To be filled by O.E.M. To be filled by O.E.M./M5A97 R2.0, BIOS 2603 06/26/2015 [ 141.965778] Call Trace: [ 141.965782] dump_stack+0x68/0x92 [ 141.965785] lockdep_rcu_suspicious+0xf7/0x100 [ 141.965788] ___might_sleep+0x56/0x1fc [ 141.965790] __might_sleep+0x68/0x6f [ 141.965793] __mutex_lock+0x4e/0x7b5 [ 141.965817] ? amdgpu_bo_list_get+0xa4/0x109 [amdgpu] [ 141.965820] ? lock_acquire+0x125/0x1b9 [ 141.965844] ? amdgpu_bo_list_set+0x464/0x464 [amdgpu] [ 141.965846] mutex_lock_nested+0x16/0x18 [ 141.965848] ? mutex_lock_nested+0x16/0x18 [ 141.965872] amdgpu_bo_list_get+0xa4/0x109 [amdgpu] [ 141.965895] amdgpu_cs_ioctl+0x4a0/0x17dd [amdgpu] [ 141.965898] ? radix_tree_node_alloc.constprop.11+0x77/0xab [ 141.965916] drm_ioctl+0x264/0x393 [drm] [ 141.965939] ? amdgpu_cs_find_mapping+0x83/0x83 [amdgpu] [ 141.965942] ? trace_hardirqs_on_caller+0x16a/0x186 Signed-off-by: Alex Xie --- drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c | 12 +--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c index dc87962..e5d61fe 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c @@ -198,12 +198,18 @@ amdgpu_bo_list_get(struct amdgpu_fpriv *fpriv, int id) result = idr_find(>bo_list_handles, id); if (result) { -if (kref_get_unless_zero(>refcount)) +if (kref_get_unless_zero(>refcount)) { +rcu_read_unlock(); mutex_lock(>lock); -else +} +else { don't need another line, just like } else { +rcu_read_unlock(); result = NULL; +} +} +else { don't need another line, just like } else { +rcu_read_unlock(); } -rcu_read_unlock(); return result; } ___ amd-gfx mailing list amd-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/amd-gfx ___ amd-gfx mailing list amd-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/amd-gfx
Re: [PATCH] drm/amdgpu: Fix blocking in RCU critical section(v2)
one small nit pick, with that fix, Reviewed-by: Chunming ZhouOn 2017年07月20日 10:46, Alex Xie wrote: In RCU read-side critical sections, blocking or sleeping is prohibited. v2: Unlock RCU for the code path where result==NULL. (David Zhou) Update subject Tested-by and reported by: Dave Airlie [ 141.965723] = [ 141.965724] WARNING: suspicious RCU usage [ 141.965726] 4.12.0-rc7 #221 Not tainted [ 141.965727] - [ 141.965728] /home/airlied/devel/kernel/linux-2.6/include/linux/rcupdate.h:531 Illegal context switch in RCU read-side critical section! [ 141.965730] other info that might help us debug this: [ 141.965731] rcu_scheduler_active = 2, debug_locks = 0 [ 141.965732] 1 lock held by amdgpu_cs:0/1332: [ 141.965733] #0: (rcu_read_lock){..}, at: [] amdgpu_bo_list_get+0x0/0x109 [amdgpu] [ 141.965774] stack backtrace: [ 141.965776] CPU: 6 PID: 1332 Comm: amdgpu_cs:0 Not tainted 4.12.0-rc7 #221 [ 141.965777] Hardware name: To be filled by O.E.M. To be filled by O.E.M./M5A97 R2.0, BIOS 2603 06/26/2015 [ 141.965778] Call Trace: [ 141.965782] dump_stack+0x68/0x92 [ 141.965785] lockdep_rcu_suspicious+0xf7/0x100 [ 141.965788] ___might_sleep+0x56/0x1fc [ 141.965790] __might_sleep+0x68/0x6f [ 141.965793] __mutex_lock+0x4e/0x7b5 [ 141.965817] ? amdgpu_bo_list_get+0xa4/0x109 [amdgpu] [ 141.965820] ? lock_acquire+0x125/0x1b9 [ 141.965844] ? amdgpu_bo_list_set+0x464/0x464 [amdgpu] [ 141.965846] mutex_lock_nested+0x16/0x18 [ 141.965848] ? mutex_lock_nested+0x16/0x18 [ 141.965872] amdgpu_bo_list_get+0xa4/0x109 [amdgpu] [ 141.965895] amdgpu_cs_ioctl+0x4a0/0x17dd [amdgpu] [ 141.965898] ? radix_tree_node_alloc.constprop.11+0x77/0xab [ 141.965916] drm_ioctl+0x264/0x393 [drm] [ 141.965939] ? amdgpu_cs_find_mapping+0x83/0x83 [amdgpu] [ 141.965942] ? trace_hardirqs_on_caller+0x16a/0x186 Signed-off-by: Alex Xie --- drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c | 12 +--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c index dc87962..e5d61fe 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c @@ -198,12 +198,18 @@ amdgpu_bo_list_get(struct amdgpu_fpriv *fpriv, int id) result = idr_find(>bo_list_handles, id); if (result) { - if (kref_get_unless_zero(>refcount)) + if (kref_get_unless_zero(>refcount)) { + rcu_read_unlock(); mutex_lock(>lock); - else + } + else { don't need another line, just like } else { + rcu_read_unlock(); result = NULL; + } + } + else { don't need another line, just like } else { + rcu_read_unlock(); } - rcu_read_unlock(); return result; } ___ amd-gfx mailing list amd-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/amd-gfx
[PATCH] drm/amdgpu: Fix blocking in RCU critical section(v2)
In RCU read-side critical sections, blocking or sleeping is prohibited. v2: Unlock RCU for the code path where result==NULL. (David Zhou) Update subject Tested-by and reported by: Dave Airlie[ 141.965723] = [ 141.965724] WARNING: suspicious RCU usage [ 141.965726] 4.12.0-rc7 #221 Not tainted [ 141.965727] - [ 141.965728] /home/airlied/devel/kernel/linux-2.6/include/linux/rcupdate.h:531 Illegal context switch in RCU read-side critical section! [ 141.965730] other info that might help us debug this: [ 141.965731] rcu_scheduler_active = 2, debug_locks = 0 [ 141.965732] 1 lock held by amdgpu_cs:0/1332: [ 141.965733] #0: (rcu_read_lock){..}, at: [] amdgpu_bo_list_get+0x0/0x109 [amdgpu] [ 141.965774] stack backtrace: [ 141.965776] CPU: 6 PID: 1332 Comm: amdgpu_cs:0 Not tainted 4.12.0-rc7 #221 [ 141.965777] Hardware name: To be filled by O.E.M. To be filled by O.E.M./M5A97 R2.0, BIOS 2603 06/26/2015 [ 141.965778] Call Trace: [ 141.965782] dump_stack+0x68/0x92 [ 141.965785] lockdep_rcu_suspicious+0xf7/0x100 [ 141.965788] ___might_sleep+0x56/0x1fc [ 141.965790] __might_sleep+0x68/0x6f [ 141.965793] __mutex_lock+0x4e/0x7b5 [ 141.965817] ? amdgpu_bo_list_get+0xa4/0x109 [amdgpu] [ 141.965820] ? lock_acquire+0x125/0x1b9 [ 141.965844] ? amdgpu_bo_list_set+0x464/0x464 [amdgpu] [ 141.965846] mutex_lock_nested+0x16/0x18 [ 141.965848] ? mutex_lock_nested+0x16/0x18 [ 141.965872] amdgpu_bo_list_get+0xa4/0x109 [amdgpu] [ 141.965895] amdgpu_cs_ioctl+0x4a0/0x17dd [amdgpu] [ 141.965898] ? radix_tree_node_alloc.constprop.11+0x77/0xab [ 141.965916] drm_ioctl+0x264/0x393 [drm] [ 141.965939] ? amdgpu_cs_find_mapping+0x83/0x83 [amdgpu] [ 141.965942] ? trace_hardirqs_on_caller+0x16a/0x186 Signed-off-by: Alex Xie --- drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c | 12 +--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c index dc87962..e5d61fe 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c @@ -198,12 +198,18 @@ amdgpu_bo_list_get(struct amdgpu_fpriv *fpriv, int id) result = idr_find(>bo_list_handles, id); if (result) { - if (kref_get_unless_zero(>refcount)) + if (kref_get_unless_zero(>refcount)) { + rcu_read_unlock(); mutex_lock(>lock); - else + } + else { + rcu_read_unlock(); result = NULL; + } + } + else { + rcu_read_unlock(); } - rcu_read_unlock(); return result; } -- 2.7.4 ___ amd-gfx mailing list amd-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/amd-gfx