linux.git/net/core/netpoll.c, branch v6.11

netpoll: do not export netpoll_poll_[disable|enable]()

2024-08-22T00:31:28+00:00

netpoll_poll_disable() and netpoll_poll_enable() are only used
from core networking code, there is no need to export them.

Signed-off-by: Eric Dumazet 
Reviewed-by: Simon Horman 
Link: https://patch.msgid.link/20240820162053.3870927-1-edumazet@google.com
Signed-off-by: Jakub Kicinski

netpoll: Fix race condition in netpoll_owner_active

2024-05-01T02:03:47+00:00

KCSAN detected a race condition in netpoll:

	BUG: KCSAN: data-race in net_rx_action / netpoll_send_skb
	write (marked) to 0xffff8881164168b0 of 4 bytes by interrupt on cpu 10:
	net_rx_action (./include/linux/netpoll.h:90 net/core/dev.c:6712 net/core/dev.c:6822)

	read to 0xffff8881164168b0 of 4 bytes by task 1 on cpu 2:
	netpoll_send_skb (net/core/netpoll.c:319 net/core/netpoll.c:345 net/core/netpoll.c:393)
	netpoll_send_udp (net/core/netpoll.c:?)

	value changed: 0x0000000a -> 0xffffffff

This happens because netpoll_owner_active() needs to check if the
current CPU is the owner of the lock, touching napi->poll_owner
non atomically. The ->poll_owner field contains the current CPU holding
the lock.

Use an atomic read to check if the poll owner is the current CPU.

Signed-off-by: Breno Leitao 
Link: https://lore.kernel.org/r/20240429100437.3487432-1-leitao@debian.org
Signed-off-by: Jakub Kicinski

netpoll: allocate netdev tracker right away

2023-06-15T07:21:11+00:00

Commit 5fa5ae605821 ("netpoll: add net device refcount tracker to struct netpoll")
was part of one of the initial netdev tracker introduction patches.
It added an explicit netdev_tracker_alloc() for netpoll, presumably
because the flow of the function is somewhat odd.
After most of the core networking stack was converted to use
the tracking hold() variants, netpoll's call to old dev_hold()
stands out a bit.

np is allocated by the caller and ready to use, we can use
netdev_hold() here, even tho np->ndev will only be set to
ndev inside __netpoll_setup().

Reviewed-by: Eric Dumazet 
Signed-off-by: Jakub Kicinski 
Signed-off-by: David S. Miller

net: don't let netpoll invoke NAPI if in xmit context

2023-04-02T12:26:21+00:00

Commit 0db3dc73f7a3 ("[NETPOLL]: tx lock deadlock fix") narrowed
down the region under netif_tx_trylock() inside netpoll_send_skb().
(At that point in time netif_tx_trylock() would lock all queues of
the device.) Taking the tx lock was problematic because driver's
cleanup method may take the same lock. So the change made us hold
the xmit lock only around xmit, and expected the driver to take
care of locking within ->ndo_poll_controller().

Unfortunately this only works if netpoll isn't itself called with
the xmit lock already held. Netpoll code is careful and uses
trylock(). The drivers, however, may be using plain lock().
Printing while holding the xmit lock is going to result in rare
deadlocks.

Luckily we record the xmit lock owners, so we can scan all the queues,
the same way we scan NAPI owners. If any of the xmit locks is held
by the local CPU we better not attempt any polling.

It would be nice if we could narrow down the check to only the NAPIs
and the queue we're trying to use. I don't see a way to do that now.

Reported-by: Roman Gushchin 
Fixes: 0db3dc73f7a3 ("[NETPOLL]: tx lock deadlock fix")
Signed-off-by: Jakub Kicinski 
Reviewed-by: Eric Dumazet 
Signed-off-by: David S. Miller

netpoll: Remove 4s sleep during carrier detection

2023-01-28T07:24:07+00:00

This patch removes the msleep(4s) during netpoll_setup() if the carrier
appears instantly.

Here are some scenarios where this workaround is counter-productive in
modern ages:

Servers which have BMC communicating over NC-SI via the same NIC as gets
used for netconsole. BMC will keep the PHY up, hence the carrier
appearing instantly.

The link is fibre, SERDES getting sync could happen within 0.1Hz, and
the carrier also appears instantly.

Other than that, if a driver is reporting instant carrier and then
losing it, this is probably a driver bug.

Reported-by: Michael van der Westhuizen 
Signed-off-by: Breno Leitao 
Link: https://lore.kernel.org/r/20230125185230.3574681-1-leitao@debian.org
Signed-off-by: Jakub Kicinski

net: move from strlcpy with unused retval to strscpy

2022-08-23T01:06:18+00:00

Follow the advice of the below link and prefer 'strscpy' in this
subsystem. Conversion is 1:1 because the return value is not used.
Generated by a coccinelle script.

Link: https://lore.kernel.org/r/CAHk-=wgfRnXz0W3D37d01q3JFkr_i_uTL=V6A6G1oUZcprmknw@mail.gmail.com/
Signed-off-by: Wolfram Sang 
Link: https://lore.kernel.org/r/20220818210215.8395-1-wsa+renesas@sang-engineering.com
Signed-off-by: Jakub Kicinski

net: rename reference+tracking helpers

2022-06-10T04:52:55+00:00

Netdev reference helpers have a dev_ prefix for historic
reasons. Renaming the old helpers would be too much churn
but we can rename the tracking ones which are relatively
recent and should be the default for new code.

Rename:
 dev_hold_track()    -> netdev_hold()
 dev_put_track()     -> netdev_put()
 dev_replace_track() -> netdev_ref_replace()

Link: https://lore.kernel.org/r/20220608043955.919359-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski

netpoll: add net device refcount tracker to struct netpoll

2021-12-07T00:06:02+00:00

Signed-off-by: Eric Dumazet 
Signed-off-by: Jakub Kicinski

Merge tag 'asm-generic-unaligned-5.14' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic

2021-07-02T19:43:40+00:00

Pull asm/unaligned.h unification from Arnd Bergmann:
 "Unify asm/unaligned.h around struct helper

  The get_unaligned()/put_unaligned() helpers are traditionally
  architecture specific, with the two main variants being the
  "access-ok.h" version that assumes unaligned pointer accesses always
  work on a particular architecture, and the "le-struct.h" version that
  casts the data to a byte aligned type before dereferencing, for
  architectures that cannot always do unaligned accesses in hardware.

  Based on the discussion linked below, it appears that the access-ok
  version is not realiable on any architecture, but the struct version
  probably has no downsides. This series changes the code to use the
  same implementation on all architectures, addressing the few
  exceptions separately"

Link: https://lore.kernel.org/lkml/75d07691-1e4f-741f-9852-38c0b4f520bc@synopsys.com/
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100363
Link: https://lore.kernel.org/lkml/20210507220813.365382-14-arnd@kernel.org/
Link: git://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic.git unaligned-rework-v2
Link: https://lore.kernel.org/lkml/CAHk-=whGObOKruA_bU3aPGZfoDqZM1_9wBkwREp0H0FgR-90uQ@mail.gmail.com/

* tag 'asm-generic-unaligned-5.14' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic:
  asm-generic: simplify asm/unaligned.h
  asm-generic: uaccess: 1-byte access is always aligned
  netpoll: avoid put_unaligned() on single character
  mwifiex: re-fix for unaligned accesses
  apparmor: use get_unaligned() only for multi-byte words
  partitions: msdos: fix one-byte get_unaligned()
  asm-generic: unaligned always use struct helpers
  asm-generic: unaligned: remove byteshift helpers
  powerpc: use linux/unaligned/le_struct.h on LE power7
  m68k: select CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
  sh: remove unaligned access for sh4a
  openrisc: always use unaligned-struct header
  asm-generic: use asm-generic/unaligned.h for most architectures

netpoll: don't require irqs disabled in rt kernels

2021-06-01T22:15:11+00:00

write_msg(netconsole.c:836) calls netpoll_send_udp after a call to
spin_lock_irqsave, which normally disables interrupts; but in PREEMPT_RT
this call just locks an rt_mutex without disabling irqs. In this case,
netpoll_send_udp is called with interrupts enabled.

Signed-off-by: Wander Lairson Costa 
Signed-off-by: David S. Miller