| Message ID | 20250211070447.25001-1-kuniyu@amazon.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [v1,net-next] checkpatch: Discourage a new use of rtnl_lock() variants. | expand |
On Tue, Feb 11, 2025 at 04:04:47PM +0900, Kuniyuki Iwashima wrote: > rtnl_lock() is a "Big Kernel Lock" in the networking slow path > and still serialises most of RTM_(NEW|DEL|SET)* rtnetlink requests. > > Commit 76aed95319da ("rtnetlink: Add per-netns RTNL.") started a > very large, in-progress, effort to make the RTNL lock scope per > network namespace. > > However, there are still some patches that newly use rtnl_lock(), > which is now discouraged, and we need to revisit it later. > > Let's warn about the case by checkpatch. > > The target functions are as follows: > > * rtnl_lock() > * rtnl_trylock() > * rtnl_lock_interruptible() > * rtnl_lock_killable() > > and the warning will be like: > > WARNING: A new use of rtnl_lock() variants is discouraged, try to use rtnl_net_lock(net) variants > #18: FILE: net/core/rtnetlink.c:79: > + rtnl_lock(); > > Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com> > --- > It would be nice if this patch goes through net-next.git to catch > new rtnl_lock() users by netdev CI. Reviewed-by: Simon Horman <horms@kernel.org>
On 2/11/25 8:04 AM, Kuniyuki Iwashima wrote: > rtnl_lock() is a "Big Kernel Lock" in the networking slow path > and still serialises most of RTM_(NEW|DEL|SET)* rtnetlink requests. > > Commit 76aed95319da ("rtnetlink: Add per-netns RTNL.") started a > very large, in-progress, effort to make the RTNL lock scope per > network namespace. > > However, there are still some patches that newly use rtnl_lock(), > which is now discouraged, and we need to revisit it later. > > Let's warn about the case by checkpatch. > > The target functions are as follows: > > * rtnl_lock() > * rtnl_trylock() > * rtnl_lock_interruptible() > * rtnl_lock_killable() > > and the warning will be like: > > WARNING: A new use of rtnl_lock() variants is discouraged, try to use rtnl_net_lock(net) variants > #18: FILE: net/core/rtnetlink.c:79: > + rtnl_lock(); > > Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com> > --- > It would be nice if this patch goes through net-next.git to catch > new rtnl_lock() users by netdev CI. > --- > scripts/checkpatch.pl | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl > index 7b28ad331742..09d5420436cc 100755 > --- a/scripts/checkpatch.pl > +++ b/scripts/checkpatch.pl > @@ -6995,6 +6995,12 @@ sub process { > # } > # } > > +# A new use of rtnl_lock() is discouraged as it's being converted to rtnl_net_lock(net). > + if ($line =~ /^\+.*\brtnl_(try)?lock(_interruptible|_killable)?\(\)/) { I think you need to add '\s*' just before '\(' to avoid the test being fooled by some bad formatting. Also I'm unsure if the '^\+.*' header is strictly required - it should but some/most existing tests don't use it, do you know why? Thanks, Paolo
From: Paolo Abeni <pabeni@redhat.com> Date: Thu, 13 Feb 2025 12:03:51 +0100 > > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl > > index 7b28ad331742..09d5420436cc 100755 > > --- a/scripts/checkpatch.pl > > +++ b/scripts/checkpatch.pl > > @@ -6995,6 +6995,12 @@ sub process { > > # } > > # } > > > > +# A new use of rtnl_lock() is discouraged as it's being converted to rtnl_net_lock(net). > > + if ($line =~ /^\+.*\brtnl_(try)?lock(_interruptible|_killable)?\(\)/) { > > I think you need to add '\s*' just before '\(' to avoid the test being > fooled by some bad formatting. Will add that. BTW, it's also caught by another warning. WARNING: space prohibited between function name and open parenthesis '(' #18: FILE: net/core/rtnetlink.c:79: + rtnl_lock (); > Also I'm unsure if the '^\+.*' header is strictly required - it should > but some/most existing tests don't use it, do you know why? I didn't notice but exactly, the following matches only + line. if ($line =~ /\brtnl_(try)?lock(_interruptible|_killable)?\s*\(\)/) { Looks like the '-' diff is filtered, matching '-' doesn't make sense. This function looks suspicious ? (maybe wrong, I'm not familiar with perl) ---8<--- sub raw_line { my ($linenr, $cnt) = @_; my $offset = $linenr - 1; $cnt++; my $line; while ($cnt) { $line = $rawlines[$offset++]; next if (defined($line) && $line =~ /^-/); $cnt--; } return $line; } ---8<--- Thanks!
From: Kuniyuki Iwashima <kuniyu@amazon.com> Date: Thu, 13 Feb 2025 21:10:28 +0900 > > Also I'm unsure if the '^\+.*' header is strictly required - it should > > but some/most existing tests don't use it, do you know why? > > I didn't notice but exactly, the following matches only + line. > > if ($line =~ /\brtnl_(try)?lock(_interruptible|_killable)?\s*\(\)/) { > > Looks like the '-' diff is filtered, matching '-' doesn't make sense. > > This function looks suspicious ? (maybe wrong, I'm not familiar with perl) I was wrong, this part did the filtering :) ---8<--- #ignore lines not being added next if ($line =~ /^[^\+]/); ---8<---
diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl index 7b28ad331742..09d5420436cc 100755 --- a/scripts/checkpatch.pl +++ b/scripts/checkpatch.pl @@ -6995,6 +6995,12 @@ sub process { # } # } +# A new use of rtnl_lock() is discouraged as it's being converted to rtnl_net_lock(net). + if ($line =~ /^\+.*\brtnl_(try)?lock(_interruptible|_killable)?\(\)/) { + WARN("rtnl_lock()", + "A new use of rtnl_lock() variants is discouraged, try to use rtnl_net_lock(net) variants\n" . $herecurr); + } + # strcpy uses that should likely be strscpy if ($line =~ /\bstrcpy\s*\(/) { WARN("STRCPY",
rtnl_lock() is a "Big Kernel Lock" in the networking slow path and still serialises most of RTM_(NEW|DEL|SET)* rtnetlink requests. Commit 76aed95319da ("rtnetlink: Add per-netns RTNL.") started a very large, in-progress, effort to make the RTNL lock scope per network namespace. However, there are still some patches that newly use rtnl_lock(), which is now discouraged, and we need to revisit it later. Let's warn about the case by checkpatch. The target functions are as follows: * rtnl_lock() * rtnl_trylock() * rtnl_lock_interruptible() * rtnl_lock_killable() and the warning will be like: WARNING: A new use of rtnl_lock() variants is discouraged, try to use rtnl_net_lock(net) variants #18: FILE: net/core/rtnetlink.c:79: + rtnl_lock(); Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com> --- It would be nice if this patch goes through net-next.git to catch new rtnl_lock() users by netdev CI. --- scripts/checkpatch.pl | 6 ++++++ 1 file changed, 6 insertions(+)