When calling EPOLL_CTL_ADD for an epoll file descriptor that is attached
directly to a wakeup source, we do not need to take the global 'epmutex',
unless the epoll file descriptor is nested. The purpose of taking the
'epmutex' on add is to prevent complex topologies such as loops and deep
wakeup paths from forming in parallel through multiple EPOLL_CTL_ADD
operations. However, for the simple case of an epoll file descriptor
attached directly to a wakeup source (with no nesting), we do not need to
hold the 'epmutex'.
This patch along with 'epoll: optimize EPOLL_CTL_DEL using rcu' improves
scalability on larger systems. Quoting Nathan Zimmer's mail on SPECjbb
performance:
"On the 16 socket run the performance went from 35k jOPS to 125k jOPS. In
addition the benchmark when from scaling well on 10 sockets to scaling
well on just over 40 sockets.
...
Currently the benchmark stops scaling at around 40-44 sockets but it seems like
I found a second unrelated bottleneck."
[akpm@linux-foundation.org: use `bool' for boolean variables, remove unneeded/undesirable cast of void*, add missed ep_scan_ready_list() kerneldoc]
Signed-off-by: Jason Baron <jbaron@akamai.com>
Tested-by: Nathan Zimmer <nzimmer@sgi.com>
Cc: Eric Wong <normalperson@yhbt.net>
Cc: Nelson Elhage <nelhage@nelhage.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Davide Libenzi <davidel@xmailserver.org>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Nathan Zimmer found that once we get over 10+ cpus, the scalability of
SPECjbb falls over due to the contention on the global 'epmutex', which is
taken in on EPOLL_CTL_ADD and EPOLL_CTL_DEL operations.
Patch #1 removes the 'epmutex' lock completely from the EPOLL_CTL_DEL path
by using rcu to guard against any concurrent traversals.
Patch #2 remove the 'epmutex' lock from EPOLL_CTL_ADD operations for
simple topologies. IE when adding a link from an epoll file descriptor to
a wakeup source, where the epoll file descriptor is not nested.
This patch (of 2):
Optimize EPOLL_CTL_DEL such that it does not require the 'epmutex' by
converting the file->f_ep_links list into an rcu one. In this way, we can
traverse the epoll network on the add path in parallel with deletes.
Since deletes can't create loops or worse wakeup paths, this is safe.
This patch in combination with the patch "epoll: Do not take global 'epmutex'
for simple topologies", shows a dramatic performance improvement in
scalability for SPECjbb.
Signed-off-by: Jason Baron <jbaron@akamai.com>
Tested-by: Nathan Zimmer <nzimmer@sgi.com>
Cc: Eric Wong <normalperson@yhbt.net>
Cc: Nelson Elhage <nelhage@nelhage.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Davide Libenzi <davidel@xmailserver.org>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
CC: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Naked use sscanf can be troublesome because the pointed to variables may
not have been set.
Add a warning when the sscanf return value is not used.
For now, do not add __must_check to the sscanf prototype because that will
cause a couple of hundred new warnings when compiling a kernel.
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Avoid prescribing kernel styled shortcuts for gcc extensions of
__attribute__((foo)) in the uapi include paths.
Fix $realfile filename when using -f/--file to not remove first level
directory as if the filename was used in a -P1 patch. Only strip the
first level directory (typically a or b) for P1 patches.
Signed-off-by: Joe Perches <joe@perches.com>
Cc: "Dixit, Ashutosh" <ashutosh.dixit@intel.com>
Cc: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Find a few more cases where parentheses are used around the value of a
return statement.
This now uses the "$balanced_parens" test and also makes the test depend
on perl v5.10 and higher.
This now finds return with parenthesis uses the old code did not find
like:
ERROR: return is not a function, parentheses are not required
#211: FILE: arch/m68k/include/asm/sun3xflop.h:211:
+ return ((error == 0) ? 0 : -1);
Signed-off-by: Joe Perches <joe@perches.com>
Tested-by: David Cohen <david.a.cohen@linux.intel.com>
Acked-by: David Cohen <david.a.cohen@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Kernel maintainers reject new instances of the GPL boilerplate paragraph
directing people to write to the FSF for a copy of the GPL, since the FSF
has moved in the past and may do so again.
Make this an error for new code, but just a --strict CHK in --file mode;
anyone interested in doing tree-wide cleanups of this form can enable this
test explicitly.
Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Peter Zijlstra prefers that comments be required near uses of memory
barriers.
Change the message level for memory barrier uses from a --strict test only
to a normal WARN so it's always emitted.
This might produce false positives around insertions of memory barriers
when a comment is outside the patch context block.
And checkpatch is still stupid, it only looks for existence of any
comment, not at the comment content.
Signed-off-by: Joe Perches <joe@perches.com>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Oliver Neukum <oliver@neukum.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
People get this regularly wrong and it breaks the LTO builds, as it causes
a section attribute conflict.
Add --fix capability too.
Based on a patch from Andi Kleen.
Signed-off-by: Joe Perches <joe@perches.com>
Cc: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
seq_vprintf, seq_printf and seq_puts are logging functions and should be
allowed to exceed the maximium line length.
Add maximum line length exceptions for these functions.
Also, suggesting seq_printf conversions to seq_puts should be tested for
arguments after the format.
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Extend the CamelCase words found to include structure members.
In https://lkml.org/lkml/2013/9/3/318 Sarah Sharp (mostly) wrote:
"In general, if checkpatch.pl complains about a variable a patch
introduces that's CamelCase, you should pay attention to it. Otherwise,
[] ignore it."
So, if checking a patch, scan the original patched file if it's available
and add any preexisting CamelCase types so reuses do not generate
CamelCase messages.
That also means Andrew's not so cruelly spurned anymore.
https://lkml.org/lkml/2013/2/22/426
Signed-off-by: Joe Perches <joe@perches.com>
Suggested-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Spaces around trigraphs are specified by CodingStyle but checkpatch is
currently silent about them because there are many current instances
without them.
Make missing spaces around trigraphs a --strict message.
Signed-off-by: Joe Perches <joe@perches.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add two trivial helpers list_next_entry() and list_prev_entry(), they
can have a lot of users including list.h itself. In fact the 1st one is
already defined in events/core.c and bnx2x_sp.c, so the patch simply
moves the definition to list.h.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Eilon Greenstein <eilong@broadcom.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Clean up probe error handling by checking parameters before any
allocations and removing an obsolete error label. Also remove unnecessary
reset of private gpio number.
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Acked-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
