| Message ID | a39407f84031eaeed5e65a7aab515a079edf5fcc.1598023524.git.tomersamara98@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | staging: android: Remove BUG/BUG_ON from ion | expand |
On Fri, Aug 21, 2020 at 09:25:26AM -0700, Randy Dunlap wrote: > On 8/21/20 8:28 AM, Tomer Samara wrote: > > Remove BUG() from ion_sytem_heap.c > > > > this fix the following checkpatch issue: > > Avoid crashing the kernel - try using WARN_ON & > > recovery code ratherthan BUG() or BUG_ON(). > > > > Signed-off-by: Tomer Samara <tomersamara98@gmail.com> > > --- > > drivers/staging/android/ion/ion_system_heap.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/staging/android/ion/ion_system_heap.c b/drivers/staging/android/ion/ion_system_heap.c > > index eac0632ab4e8..00d6154aec34 100644 > > --- a/drivers/staging/android/ion/ion_system_heap.c > > +++ b/drivers/staging/android/ion/ion_system_heap.c > > @@ -30,7 +30,7 @@ static int order_to_index(unsigned int order) > > for (i = 0; i < NUM_ORDERS; i++) > > if (order == orders[i]) > > return i; > > - BUG(); > > + /* This is impossible. */ > > return -1; > > } > > Hi, > Please explain why this is impossible. > > If some caller calls order_to_index(5), it will return -1, yes? > > -- > ~Randy > As Dan Carpenter says here https://lkml.kernel.org/lkml/cover.1597865771.git.tomersamara98@gmail.com/T/#mc790b91029565b1bb0cb87997b39007d9edb6e04. After looking at callers we see that order_to_index called from 2 functions: - alloc_buffer_page called from alloc_largest_available which loop over all legit order nubmers ( Flow: alloc_largest_available-->alloc_buffer_page-->order_to_index ) - free_buffer_page takes the order using compound_order, which return 0 or the order number for the page, this function has 2 callers too, ion_system_heap_allocate (which called it in case of failure at sg_alloc_table, thus calling from this flow will no casue error) and ion_system_heap_free (which will be called on every sg table in the buffer that allocated good, meaning from this flow also error will not be created). ( Flows: ion_system_heap_free --> free_buffer_page --> order_to_index ion_system_heap_allocate --> free_buffer_page --> order_to_index ) Of course if some user will use this function with wrong order number he will be able to get this -1. So should I remove this comment and resotre the error checks? Btw, this is the same reason that I dropped the error check at ion_page_pool_shrink, so should I restore here also? Thanks, Tomer Samara
On 8/22/20 2:34 AM, Tomer Samara wrote: > On Fri, Aug 21, 2020 at 09:25:26AM -0700, Randy Dunlap wrote: >> On 8/21/20 8:28 AM, Tomer Samara wrote: >>> Remove BUG() from ion_sytem_heap.c >>> >>> this fix the following checkpatch issue: >>> Avoid crashing the kernel - try using WARN_ON & >>> recovery code ratherthan BUG() or BUG_ON(). >>> >>> Signed-off-by: Tomer Samara <tomersamara98@gmail.com> >>> --- >>> drivers/staging/android/ion/ion_system_heap.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/drivers/staging/android/ion/ion_system_heap.c b/drivers/staging/android/ion/ion_system_heap.c >>> index eac0632ab4e8..00d6154aec34 100644 >>> --- a/drivers/staging/android/ion/ion_system_heap.c >>> +++ b/drivers/staging/android/ion/ion_system_heap.c >>> @@ -30,7 +30,7 @@ static int order_to_index(unsigned int order) >>> for (i = 0; i < NUM_ORDERS; i++) >>> if (order == orders[i]) >>> return i; >>> - BUG(); >>> + /* This is impossible. */ >>> return -1; >>> } >> >> Hi, >> Please explain why this is impossible. >> >> If some caller calls order_to_index(5), it will return -1, yes? >> >> -- >> ~Randy >> > > As Dan Carpenter says here https://lkml.kernel.org/lkml/cover.1597865771.git.tomersamara98@gmail.com/T/#mc790b91029565b1bb0cb87997b39007d9edb6e04. > After looking at callers we see that order_to_index called from 2 functions: > - alloc_buffer_page called from alloc_largest_available which > loop over all legit order nubmers > ( Flow: > alloc_largest_available-->alloc_buffer_page-->order_to_index > ) > > - free_buffer_page takes the order using compound_order, which return 0 or > the order number for the page, this function has 2 callers too, > ion_system_heap_allocate (which called it in case of failure at sg_alloc_table, > thus calling from this flow will no casue error) and ion_system_heap_free > (which will be called on every sg table in the buffer that allocated good, > meaning from this flow also error will not be created). > ( Flows: > ion_system_heap_free --> free_buffer_page --> order_to_index > ion_system_heap_allocate --> free_buffer_page --> order_to_index > ) > > Of course if some user will use this function with wrong order number he will be able to get this -1. > So should I remove this comment and resotre the error checks? I think so, but that's just an opinion. > Btw, this is the same reason that I dropped the error check at ion_page_pool_shrink, so should I restore here also? IMO yes. Getting rid of BUG()s is a good goal, but usually it's not so easy. thanks.
On Fri, Aug 21, 2020 at 09:25:26AM -0700, Randy Dunlap wrote: > On 8/21/20 8:28 AM, Tomer Samara wrote: > > Remove BUG() from ion_sytem_heap.c > > > > this fix the following checkpatch issue: > > Avoid crashing the kernel - try using WARN_ON & > > recovery code ratherthan BUG() or BUG_ON(). > > > > Signed-off-by: Tomer Samara <tomersamara98@gmail.com> > > --- > > drivers/staging/android/ion/ion_system_heap.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/staging/android/ion/ion_system_heap.c b/drivers/staging/android/ion/ion_system_heap.c > > index eac0632ab4e8..00d6154aec34 100644 > > --- a/drivers/staging/android/ion/ion_system_heap.c > > +++ b/drivers/staging/android/ion/ion_system_heap.c > > @@ -30,7 +30,7 @@ static int order_to_index(unsigned int order) > > for (i = 0; i < NUM_ORDERS; i++) > > if (order == orders[i]) > > return i; > > - BUG(); > > + /* This is impossible. */ > > return -1; > > } > > Hi, > Please explain why this is impossible. > > If some caller calls order_to_index(5), it will return -1, yes? > I was happy enough with the comment as-is given that I suggested it. But an alternative comment could be "/* This is impossible. We always pass valid values to this function. */ regards, dan carpenter
On Mon, Aug 24, 2020 at 02:24:57PM +0300, Dan Carpenter wrote: > On Fri, Aug 21, 2020 at 09:25:26AM -0700, Randy Dunlap wrote: > > On 8/21/20 8:28 AM, Tomer Samara wrote: > > > Remove BUG() from ion_sytem_heap.c > > > > > > this fix the following checkpatch issue: > > > Avoid crashing the kernel - try using WARN_ON & > > > recovery code ratherthan BUG() or BUG_ON(). > > > > > > Signed-off-by: Tomer Samara <tomersamara98@gmail.com> > > > --- > > > drivers/staging/android/ion/ion_system_heap.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/drivers/staging/android/ion/ion_system_heap.c b/drivers/staging/android/ion/ion_system_heap.c > > > index eac0632ab4e8..00d6154aec34 100644 > > > --- a/drivers/staging/android/ion/ion_system_heap.c > > > +++ b/drivers/staging/android/ion/ion_system_heap.c > > > @@ -30,7 +30,7 @@ static int order_to_index(unsigned int order) > > > for (i = 0; i < NUM_ORDERS; i++) > > > if (order == orders[i]) > > > return i; > > > - BUG(); > > > + /* This is impossible. */ > > > return -1; > > > } > > > > Hi, > > Please explain why this is impossible. > > > > If some caller calls order_to_index(5), it will return -1, yes? > > > > I was happy enough with the comment as-is given that I suggested it. > But an alternative comment could be "/* This is impossible. > We always pass valid values to this function. */ Another option is to just change the BUG_ON() to a WARN_ON(). I feel like that communicates the same thing but makes checkpatch happy. regards, dan carpenter
On Mon, Aug 24, 2020 at 02:27:08PM +0300, Dan Carpenter wrote: > On Mon, Aug 24, 2020 at 02:24:57PM +0300, Dan Carpenter wrote: > > On Fri, Aug 21, 2020 at 09:25:26AM -0700, Randy Dunlap wrote: > > > On 8/21/20 8:28 AM, Tomer Samara wrote: > > > > Remove BUG() from ion_sytem_heap.c > > > > > > > > this fix the following checkpatch issue: > > > > Avoid crashing the kernel - try using WARN_ON & > > > > recovery code ratherthan BUG() or BUG_ON(). > > > > > > > > Signed-off-by: Tomer Samara <tomersamara98@gmail.com> > > > > --- > > > > drivers/staging/android/ion/ion_system_heap.c | 2 +- > > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > > > diff --git a/drivers/staging/android/ion/ion_system_heap.c b/drivers/staging/android/ion/ion_system_heap.c > > > > index eac0632ab4e8..00d6154aec34 100644 > > > > --- a/drivers/staging/android/ion/ion_system_heap.c > > > > +++ b/drivers/staging/android/ion/ion_system_heap.c > > > > @@ -30,7 +30,7 @@ static int order_to_index(unsigned int order) > > > > for (i = 0; i < NUM_ORDERS; i++) > > > > if (order == orders[i]) > > > > return i; > > > > - BUG(); > > > > + /* This is impossible. */ > > > > return -1; > > > > } > > > > > > Hi, > > > Please explain why this is impossible. > > > > > > If some caller calls order_to_index(5), it will return -1, yes? > > > > > > > I was happy enough with the comment as-is given that I suggested it. > > But an alternative comment could be "/* This is impossible. > > We always pass valid values to this function. */ > > Another option is to just change the BUG_ON() to a WARN_ON(). I feel > like that communicates the same thing but makes checkpatch happy. Actually earlier Greg pointed out that some systems have panic on warn so WARN_ON() doesn't work. Just add the comment. regards, dan carpenter
diff --git a/drivers/staging/android/ion/ion_system_heap.c b/drivers/staging/android/ion/ion_system_heap.c index eac0632ab4e8..00d6154aec34 100644 --- a/drivers/staging/android/ion/ion_system_heap.c +++ b/drivers/staging/android/ion/ion_system_heap.c @@ -30,7 +30,7 @@ static int order_to_index(unsigned int order) for (i = 0; i < NUM_ORDERS; i++) if (order == orders[i]) return i; - BUG(); + /* This is impossible. */ return -1; }
Remove BUG() from ion_sytem_heap.c this fix the following checkpatch issue: Avoid crashing the kernel - try using WARN_ON & recovery code ratherthan BUG() or BUG_ON(). Signed-off-by: Tomer Samara <tomersamara98@gmail.com> --- drivers/staging/android/ion/ion_system_heap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)