Buildresult: linus/se7619_defconfig/sh4-gcc10 built on Jul 31 2021, 10:01

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Status:	OK
Date/Time:	Jul 31 2021, 10:01
Duration:	0:00:26.521810
Builder:	ka1
Revision:	pipe: make pipe writes always wake up readers (`3a34b13a88caeb2800ab44a4918f230041b37dd9)`
Target:	linus/se7619_defconfig/sh4-gcc10
Branch:	linus
Compiler:	sh4-gcc10 (sh4-linux-gcc (GCC) 10.1.0 / GNU ld (GNU Binutils) 2.34)
Config:	se7619_defconfig (download)
Log:	Download original Possible warnings (6) <stdin>:1515:2: warning: #warning syscall clone3 not implemented [-Wcpp] include/linux/sh_intc.h:100:63: warning: division 'sizeof (void ) / sizeof (void)' does not compute the number of array elements [-Wsizeof-pointer-div] include/linux/sh_intc.h:100:63: warning: division 'sizeof (void ) / sizeof (void)' does not compute the number of array elements [-Wsizeof-pointer-div] include/linux/sh_intc.h:100:63: warning: division 'sizeof (void ) / sizeof (void)' does not compute the number of array elements [-Wsizeof-pointer-div] include/linux/sh_intc.h:100:63: warning: division 'sizeof (void ) / sizeof (void)' does not compute the number of array elements [-Wsizeof-pointer-div] drivers/tty/serial/sh-sci.c:2657:19: warning: unused variable 'sport' [-Wunused-variable] Full Log # git rev-parse -q --verify 3a34b13a88caeb2800ab44a4918f230041b37dd9^{commit} 3a34b13a88caeb2800ab44a4918f230041b37dd9 already have revision, skipping fetch # git checkout -q -f -B kisskb 3a34b13a88caeb2800ab44a4918f230041b37dd9 # git clean -qxdf # < git log -1 # commit 3a34b13a88caeb2800ab44a4918f230041b37dd9 # Author: Linus Torvalds <torvalds@linux-foundation.org> # Date: Fri Jul 30 15:42:34 2021 -0700 # # pipe: make pipe writes always wake up readers # # Since commit 1b6b26ae7053 ("pipe: fix and clarify pipe write wakeup # logic") we have sanitized the pipe write logic, and would only try to # wake up readers if they needed it. # # In particular, if the pipe already had data in it before the write, # there was no point in trying to wake up a reader, since any existing # readers must have been aware of the pre-existing data already. Doing # extraneous wakeups will only cause potential thundering herd problems. # # However, it turns out that some Android libraries have misused the EPOLL # interface, and expected "edge triggered" be to "any new write will # trigger it". Even if there was no edge in sight. # # Quoting Sandeep Patil: # "The commit 1b6b26ae7053 ('pipe: fix and clarify pipe write wakeup # logic') changed pipe write logic to wakeup readers only if the pipe # was empty at the time of write. However, there are libraries that # relied upon the older behavior for notification scheme similar to # what's described in [1] # # One such library 'realm-core'[2] is used by numerous Android # applications. The library uses a similar notification mechanism as GNU # Make but it never drains the pipe until it is full. When Android moved # to v5.10 kernel, all applications using this library stopped working. # # The library has since been fixed[3] but it will be a while before all # applications incorporate the updated library" # # Our regression rule for the kernel is that if applications break from # new behavior, it's a regression, even if it was because the application # did something patently wrong. Also note the original report [4] by # Michal Kerrisk about a test for this epoll behavior - but at that point # we didn't know of any actual broken use case. # # So add the extraneous wakeup, to approximate the old behavior. # # [ I say "approximate", because the exact old behavior was to do a wakeup # not for each write(), but for each pipe buffer chunk that was filled # in. The behavior introduced by this change is not that - this is just # "every write will cause a wakeup, whether necessary or not", which # seems to be sufficient for the broken library use. ] # # It's worth noting that this adds the extraneous wakeup only for the # write side, while the read side still considers the "edge" to be purely # about reading enough from the pipe to allow further writes. # # See commit f467a6a66419 ("pipe: fix and clarify pipe read wakeup logic") # for the pipe read case, which remains that "only wake up if the pipe was # full, and we read something from it". # # Link: https://lore.kernel.org/lkml/CAHk-=wjeG0q1vgzu4iJhW5juPkTsjTYmiqiMUYAebWW+0bam6w@mail.gmail.com/ [1] # Link: https://github.com/realm/realm-core [2] # Link: https://github.com/realm/realm-core/issues/4666 [3] # Link: https://lore.kernel.org/lkml/CAKgNAkjMBGeAwF=2MKK758BhxvW58wYTgYKB2V-gY1PwXxrH+Q@mail.gmail.com/ [4] # Link: https://lore.kernel.org/lkml/20210729222635.2937453-1-sspatil@android.com/ # Reported-by: Sandeep Patil <sspatil@android.com> # Cc: Michael Kerrisk <mtk.manpages@gmail.com> # Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> # < /opt/cross/kisskb/korg/gcc-10.1.0-nolibc/sh4-linux/bin/sh4-linux-gcc --version # < /opt/cross/kisskb/korg/gcc-10.1.0-nolibc/sh4-linux/bin/sh4-linux-ld --version # < git log --format=%s --max-count=1 3a34b13a88caeb2800ab44a4918f230041b37dd9 # < make -s -j 48 ARCH=sh O=/kisskb/build/linus_se7619_defconfig_sh4-gcc10 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-10.1.0-nolibc/sh4-linux/bin/sh4-linux- se7619_defconfig # < make -s -j 48 ARCH=sh O=/kisskb/build/linus_se7619_defconfig_sh4-gcc10 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-10.1.0-nolibc/sh4-linux/bin/sh4-linux- help # make -s -j 48 ARCH=sh O=/kisskb/build/linus_se7619_defconfig_sh4-gcc10 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-10.1.0-nolibc/sh4-linux/bin/sh4-linux- olddefconfig # make -s -j 48 ARCH=sh O=/kisskb/build/linus_se7619_defconfig_sh4-gcc10 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-10.1.0-nolibc/sh4-linux/bin/sh4-linux- Generating include/generated/machtypes.h <stdin>:1515:2: warning: #warning syscall clone3 not implemented [-Wcpp] In file included from /kisskb/src/arch/sh/include/asm/hw_irq.h:6, from /kisskb/src/include/linux/irq.h:591, from /kisskb/src/include/asm-generic/hardirq.h:17, from /kisskb/src/arch/sh/include/asm/hardirq.h:9, from /kisskb/src/include/linux/hardirq.h:11, from /kisskb/src/include/linux/interrupt.h:11, from /kisskb/src/include/linux/serial_core.h:13, from /kisskb/src/include/linux/serial_sci.h:6, from /kisskb/src/arch/sh/kernel/cpu/sh2/setup-sh7619.c:11: /kisskb/src/include/linux/sh_intc.h:100:63: warning: division 'sizeof (void ) / sizeof (void)' does not compute the number of array elements [-Wsizeof-pointer-div] 100 \| #define _INTC_ARRAY(a) a, __same_type(a, NULL) ? 0 : sizeof(a)/sizeof(a) \| ^ /kisskb/src/include/linux/sh_intc.h:105:24: note: in expansion of macro '_INTC_ARRAY' 105 \| _INTC_ARRAY(vectors), _INTC_ARRAY(groups), \ \| ^~~~~~~~~~~ /kisskb/src/include/linux/sh_intc.h:124:8: note: in expansion of macro 'INTC_HW_DESC' 124 \| .hw = INTC_HW_DESC(vectors, groups, mask_regs, \ \| ^~~~~~~~~~~~ /kisskb/src/arch/sh/kernel/cpu/sh2/setup-sh7619.c:58:8: note: in expansion of macro 'DECLARE_INTC_DESC' 58 \| static DECLARE_INTC_DESC(intc_desc, "sh7619", vectors, NULL, \| ^~~~~~~~~~~~~~~~~ /kisskb/src/include/linux/sh_intc.h:100:63: warning: division 'sizeof (void ) / sizeof (void)' does not compute the number of array elements [-Wsizeof-pointer-div] 100 \| #define _INTC_ARRAY(a) a, __same_type(a, NULL) ? 0 : sizeof(a)/sizeof(a) \| ^ /kisskb/src/include/linux/sh_intc.h:106:2: note: in expansion of macro '_INTC_ARRAY' 106 \| _INTC_ARRAY(mask_regs), _INTC_ARRAY(prio_regs), \ \| ^~~~~~~~~~~ /kisskb/src/include/linux/sh_intc.h:124:8: note: in expansion of macro 'INTC_HW_DESC' 124 \| .hw = INTC_HW_DESC(vectors, groups, mask_regs, \ \| ^~~~~~~~~~~~ /kisskb/src/arch/sh/kernel/cpu/sh2/setup-sh7619.c:58:8: note: in expansion of macro 'DECLARE_INTC_DESC' 58 \| static DECLARE_INTC_DESC(intc_desc, "sh7619", vectors, NULL, \| ^~~~~~~~~~~~~~~~~ /kisskb/src/include/linux/sh_intc.h:100:63: warning: division 'sizeof (void ) / sizeof (void)' does not compute the number of array elements [-Wsizeof-pointer-div] 100 \| #define _INTC_ARRAY(a) a, __same_type(a, NULL) ? 0 : sizeof(a)/sizeof(a) \| ^ /kisskb/src/include/linux/sh_intc.h:107:2: note: in expansion of macro '_INTC_ARRAY' 107 \| _INTC_ARRAY(sense_regs), _INTC_ARRAY(ack_regs), \ \| ^~~~~~~~~~~ /kisskb/src/include/linux/sh_intc.h:124:8: note: in expansion of macro 'INTC_HW_DESC' 124 \| .hw = INTC_HW_DESC(vectors, groups, mask_regs, \ \| ^~~~~~~~~~~~ /kisskb/src/arch/sh/kernel/cpu/sh2/setup-sh7619.c:58:8: note: in expansion of macro 'DECLARE_INTC_DESC' 58 \| static DECLARE_INTC_DESC(intc_desc, "sh7619", vectors, NULL, \| ^~~~~~~~~~~~~~~~~ /kisskb/src/include/linux/sh_intc.h:100:63: warning: division 'sizeof (void ) / sizeof (void)' does not compute the number of array elements [-Wsizeof-pointer-div] 100 \| #define _INTC_ARRAY(a) a, __same_type(a, NULL) ? 0 : sizeof(a)/sizeof(a) \| ^ /kisskb/src/include/linux/sh_intc.h:107:27: note: in expansion of macro '_INTC_ARRAY' 107 \| _INTC_ARRAY(sense_regs), _INTC_ARRAY(ack_regs), \ \| ^~~~~~~~~~~ /kisskb/src/include/linux/sh_intc.h:124:8: note: in expansion of macro 'INTC_HW_DESC' 124 \| .hw = INTC_HW_DESC(vectors, groups, mask_regs, \ \| ^~~~~~~~~~~~ /kisskb/src/arch/sh/kernel/cpu/sh2/setup-sh7619.c:58:8: note: in expansion of macro 'DECLARE_INTC_DESC' 58 \| static DECLARE_INTC_DESC(intc_desc, "sh7619", vectors, NULL, \| ^~~~~~~~~~~~~~~~~ /kisskb/src/drivers/tty/serial/sh-sci.c: In function 'sci_remap_port': /kisskb/src/drivers/tty/serial/sh-sci.c:2657:19: warning: unused variable 'sport' [-Wunused-variable] 2657 \| struct sci_port *sport = to_sci_port(port); \| ^~~~~ Completed OK # rm -rf /kisskb/build/linus_se7619_defconfig_sh4-gcc10 # Build took: 0:00:26.521810

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